Opacity
O•pac´i•ty, n. [L. opacitas: cf.F. opacite.]
1. The state of being opaque; the quality of a body which renders it impervious to the rays of light; want of transparency; opaqueness.
2. Obscurity; want of clearness. Bp. Hall.

Opacous
O•pa´cous, a. [L. opacus. See Opaque.] Opaque. [R.] Milton. — O•pa´cous•ness, n. [R.]

Opah
O´pah, n. (Zoöl.) A large oceanic fish ( Lampris quttatus), inhabiting the Atlantic Ocean. It is remarkable for its brilliant colors, which are red, green, and blue, with tints of purple and gold, covered with round silvery spots. Called also king of the herrings.

Opake
O•pake´, a. See Opaque.

Opalesce
O•pal•esce´, v. i. [ imp. & p. p. Opalesced p. pr. & vb. n. Opalescing ] To give forth a play of colors, like the opal.

Opalescent
O•pal•es´cent, a. Reflecting a milky or pearly light from the interior; having an opaline play of colors.

Opaline
O´pal•ine, a. [Cf. F. opalin.] Of, pertaining to, or like, opal in appearance; having changeable colors like those of the opal.

Opaline
O´pal•ine, n.
1. An opaline variety of yellow chalcedony.
2. Opal glass.
3. An opaline color or expanse.

Opalize
O´pal•ize, v. t. [ imp. & p. p. Opalized p. pr. & vb. n. Opalizing.] [Cf. F. opaliser.] To convert into opal, or a substance like opal. Lyell.

Opaque
O•paque´, a. [F., fr. L. opacus. Cf. Opacous.]
1. Impervious to the rays of light; not transparent; as an opaque substance.
2. Obscure; not clear; unintelligible. [Colloq.]

Opaque
O•paque´, n. That which is opaque; opacity. Young.

Opaqueness
O•paque´ness, n. The state or quality of being impervious to light; opacity. Dr. H. More.

Ope, a. Open. [Poetic] Spenser.
"On Sunday heaven’s gate stands ope." Herbert.

Ope, v. t. & i. To open. [Poetic]
"Wilt thou not ope thy heart to know What rainbows teach and sunsets show?" Emerson.

Opeidoscope
O•pei´do•scope, n. [Gr.,, voice + form + -scope.] (Physics) An instrument, consisting of a tube having one end open and the other end covered with a thin flexible membrance to the center of which is attached a small mirror. It is used for exhibiting upon a screen, by means of rays reflected from the mirror, the vibratory motions caused by sounds produced at the open end of the tube, as by speaking or singing into it. A. E. Dolbear.

Opelet
Ope´let, n. (Zoöl.) A bright-colored European actinian ( Anemonia, or Anthea, sulcata); — so called because it does not retract its tentacles.

Open
O´pen, a. [AS. open; akin to D. open, OS. opan, G. offan, Icel. opinn, Sw. öppen, Dan. aaben, and perh. to E. up. Cf. Up, and Ope.]
1. Free of access; not shut up; not closed; affording unobstructed ingress or egress; not impeding or preventing passage; not locked up or covered over; — applied to passageways; as an open door, window, road, etc.; also to inclosed structures or objects; as open houses, boxes, baskets, bottles, etc.; also to means of communication or approach by water or land; as an open harbor or roadstead.
"Through the gate, Wide open and unquarded, Satan passed." Milton also figuratively, used of the ways of communication of the mind, as by the senses; ready to hear, see, etc.; as to keep one’s eyes and ears open.
"His ears are open unto their cry." Ps. xxxiv. 15.
2. Free to be used, enjoyed, visited, or the like; not private; public; unrestricted in use; as an open library, museum, court, or other assembly; liable to the approach, trespass, or attack of any one; unprotected; exposed.
"If Demetrius … have a matter against any man, the law is open and there are deputies." Acts xix. 33.
"The service that I truly did his life, Hath left me open to all injuries." Shak.
3. Free or cleared of obstruction to progress or to view; accessible; as an open tract; the open sea.
4. Not drawn together, closed, or contracted; extended; expanded; as an open hand; open arms; an open flower; an open prospect.
"Each, with open arms, embraced her chosen knight." Dryden.
5. Hence: (a) Without reserve or false pretense; sincere; characterized by sincerity; unfeigned; frank; also generous; liberal; bounteous; — applied to personal appearance, or character, and to the expression of thought and feeling, etc.
"With aspect open, shall erect his head." Pope.
"The Moor is of a free and open nature." Shak.
"The French are always open, familiar, and talkative." Addison. (b) Not concealed or secret; not hidden or disguised; exposed to view or to knowledge; revealed; apparent; as open schemes or plans; open shame or guilt.
"His thefts are too open." Shak.
"That I may find him, and with secret gaze Or open admiration him behold." Milton.
6. Not of a quality to prevent communication, as by closing water ways, blocking roads, etc.; hence, not frosty or inclement; mild; — used of the weather or the climate; as an open season; an open winter. Bacon.
7. Not settled or adjusted; not decided or determined; not closed or withdrawn from consideration; as an open account; an open question; to keep an offer or opportunity open.
8. Free; disengaged; unappropriated; as to keep a day open for any purpose; to be open for an engagement.
9. (Phon.) (a) Uttered with a relatively wide opening of the articulating organs; — said of vowels; as the än fär is open as compared with the a in say. (b) Uttered, as a consonant, with the oral passage simply narrowed without closure, as in uttering s.
10. (Mus.) (a) Not closed or stopped with the finger; — said of the string of an instrument, as of a violin, when it is allowed to vibrate throughout its whole length. (b) Produced by an open string; as an open tone. The open air, the air out of doors. — Open chain. (Chem.) See Closed chain, under Chain. — Open circuit (Elec.), a conducting circuit which is incomplete, or interrupted at some point; — opposed to an uninterrupted, or closed circuit. — Open communion, communion in the Lord’s supper not restricted to persons who have been baptized by immersion. Cf. Close communion, under Close, a. — Open diapason (Mus.), a certain stop in an organ, in which the pipes or tubes are formed like the mouthpiece of a flageolet at the end where the wind enters, and are open at the other end. — Open flank (Fort.), the part of the flank covered by the orillon. — Open-front furnace (Metal.), a blast furnace having a forehearth. — Open harmony (Mus.), harmony the tones of which are widely dispersed, or separated by wide intervals. — Open hawse (Naut.), a hawse in which the cables are parallel or slightly divergent. Cf. Foul hawse, under Hawse. — Open hearth (Metal.), the shallow hearth of a reverberatory furnace. — Open-hearth furnace, a reverberatory furnace; esp., a kind of reverberatory furnace in which the fuel is gas used in manufacturing steel. — Open-hearth process (Steel Manuf.), a process by which melted cast iron is converted into steel by the addition of wrought iron, or iron ore and manganese, and by exposure to heat in an open-hearth furnace; — also called the Siemens- Martin process, from the inventors. — Open-hearth steel, steel made by an open-hearth process; — also called Siemens-Martin steel. — Open newel. (Arch.) See Hollow newel, under Hollow. — Open pipe (Mus.), a pipe open at the top. It has a pitch about an octave higher than a closed pipe of the same length. — Open- timber roof (Arch.), a roof of which the constructional parts, together with the under side of the covering, or its lining, are treated ornamentally, and left to form the ceiling of an apartment below, as in a church, a public hall, and the like. — Open vowel or consonant. See Open, a. , 9. Open is used in many compounds, most of which are self-explaining; as open-breasted, open-minded.
Syn. — Unclosed; uncovered; unprotected; exposed; plain; apparent; obvious; evident; public; unreserved; frank; sincere; undissembling; artless. See Candid, and Ingenuous.

Open
O´pen, n. Open or unobstructed space; clear land, without trees or obstructions; open ocean; open water. "To sail into the open." Jowett (Thucyd. ).
"Then we got into the open." W. Black.In open, in full view; without concealment; openly. [Obs.] Beau. & Fl.

Open
O´pen v. t. [ imp. & p. p. Opened p. pr. & vb. n. Opening.] [AS. openian. See Open,a.]
1. To make or set open; to render free of access; to unclose; to unbar; to unlock; to remove any fastening or covering from; as to open a door; to open a box; to open a room; to open a letter.
"And all the windows of my heart I open to the day." Whittier.
2. To spread; to expand; as to open the hand.
3. To disclose; to reveal; to interpret; to explain.
"The king opened himself to some of his council, that he was sorry for the earl’s death." Bacon.
"Unto thee have I opened my cause." Jer. xx. 12.
"While he opened to us the Scriptures." Luke xxiv. 32.
4. To make known; to discover; also to render available or accessible for settlements, trade, etc.
"The English did adventure far for to open the North parts of America." Abp. Abbot.
5. To enter upon; to begin; as to open a discussion; to open fire upon an enemy; to open trade, or correspondence; to open a case in court, or a meeting.
6. To loosen or make less compact; as to open matted cotton by separating the fibers. To open one’s mouth, to speak. — To open up, to lay open; to discover; to disclose.
"Poetry that had opened up so many delightful views into the character and condition of our "bold peasantry, their country’s pride."" Prof. Wilson.

Open
O´pen, v. i.
1. To unclose; to form a hole, breach, or gap; to be unclosed; to be parted.
"The earth opened and swallowed up Dathan, and covered the company of Abiram." Ps. cvi. 17.
2. To expand; to spread out; to be disclosed; as the harbor opened to our view.
3. To begin; to commence; as the stock opened at par; the battery opened upon the enemy.
4. (Sporting) To bark on scent or view of the game.

Open door
O"pen door. (a) Open or free admission to all; hospitable welcome; free opportunity.
"She of the open soul and open door,With room about her hearth for all mankind." Lowell. (b) In modern diplomacy, opportunity for political and commercial intercourse open to all upon equal terms, esp. with reference to a nation whose policy is wholly or partially fixed by nations foreign to itself, or to territory newly acquired by a conquering nation. In this sense, often used adjectively, as open-door system, open-door policy, etc.
"The steps taken by Britain to maintain the open door have so far proved to be perfectly futile." A. R. Colquhoun.

Open sea. (Internat. Law) A sea open to all nations. See Mare clausum.

Open-air
O´pen-air, a. Taking place in the open air; outdoor; as an open-air game or meeting.

Openbill
O´pen•bill, n. (Zoöl.) A bird of the genus Anastomus, allied to the stork; — so called because the two parts of the bill touch only at the base and tip. One species inhabits India, another Africa. Called also open- beak. See Illust. (m), under Beak.

Open-eyed
O´pen-eyed, a. With eyes widely open; watchful; vigilant. Shak.

Open-handed
O´pen-hand•ed, a. Generous; liberal; munificent. — O´pen-hand•ed•ness, n. J. S. Mill.

Open-headed
O´pen-head•ed, a. Bareheaded. [Obs.]

Open-hearted
O´pen-heart•ed, a. Candid; frank; generous. Dryden. — O´pen-heart•ed•ly, adv. — O´pen-heart•ed•ness, n. Walton.

Open-hearth steel. See under Open.

Openly
O´pen•ly, adv. [AS. openlice.]
1. In an open manner; publicly; not in private; without secrecy.
"How grossly and openly do many of us contradict the precepts of the gospel by our ungodliness!" Tillotson.
2. Without reserve or disguise; plainly; evidently.
"My love … shall show itself more openly." Shak.

Open-mouthed
O´pen-mouthed, a. Having the mouth open; gaping; hence, greedy; clamorous. L’Estrange.

Openness
O´pen•ness, n. The quality or state of being open.

Openwork
O´pen•work, n.
1. Anything so constructed or manufactured (in needlework, carpentry, metal work, etc.) as to show openings through its substance; work that is perforated or pierced.
2. (Mining) A quarry; an open cut. Raymond.

Opera
Op´er•a, n. [It., fr. opera work, composition, opposed to an improvisation, fr. L. opera pains work, fr. opus, operis, work, labor: cf. F. opera. See Operate.]
1. A drama, either tragic or comic, of which music forms an essential part; a drama wholly or mostly sung, consisting of recitative, arials, choruses, duets, trios, etc., with orchestral accompaniment, preludes, and interludes, together with appropriate costumes, scenery, and action; a lyric drama.
2. The score of a musical drama, either written or in print; a play set to music.
3. The house where operas are exhibited. Opera bouffe [F. opera opera + bouffe comic, It. buffo], Opera buffa [It.], light, farcical, burlesque opera. — Opera box, a partially inclosed portion of the auditorium of an opera house for the use of a small private party. — Opera comique [F.], comic or humorous opera. — Opera flannel, a light flannel, highly finished. Knight. — Opera girl (Bot.), an East Indian plant ( Mantisia saltatoria) of the Ginger family, sometimes seen in hothouses. It has curious flowers which have some resemblance to a ballet dancer, whence the popular name. Called also dancing girls. — Opera glass, a short telescope with concave eye lenses of low power, usually made double, that is, with a tube and set of glasses for each eye; a lorgnette; — so called because adapted for use at the opera, theater, etc. — Opera hat, a gentleman’s folding hat. — Opera house, specifically, a theater devoted to the performance of operas. — Opera seria [It.], serious or tragic opera; grand opera.

Operameter
Op•er•am´e•ter, n. [L. opus, operis, pl. opera work + -meter.] An instrument or machine for measuring work done, especially for ascertaining the number of rotations made by a machine or wheel in manufacturing cloth; a counter. Ure. { Op´er•ance, Op´er•an•cy } n. The act of operating or working; operation. [R.]

Operand
Op´er•and, n. [From neuter of L. operandus, gerundive of operari. See Operate.] (Math.) The symbol, quantity, or thing upon which a mathematical operation is performed; — called also faciend.

Operation
Op•er•a´tion, n. [L. operatio: cf. F. operation.]
1. The act or process of operating; agency; the exertion of power, physical, mechanical, or moral.
"The pain and sickness caused by manna are the effects of its operation on the stomach." Locke.
"Speculative painting, without the assistance of manual operation, can never attain to perfection." Dryden.
2. The method of working; mode of action.
3. That which is operated or accomplished; an effect brought about in accordance with a definite plan; as military or naval operations.
4. Effect produced; influence. [Obs.]
"The bards … had great operation on the vulgar." Fuller.
5. (Math.) Something to be done; some transformation to be made upon quantities, the transformation being indicated either by rules or symbols.
6. (Surg.) Any methodical action of the hand, or of the hand with instruments, on the human body, to produce a curative or remedial effect, as in amputation, etc. Calculus of operations. See under Calculus.

Operatively
Op´er•a•tive•ly, adv. In an operative manner.

Operator
Op´er•a•tor, n. [L.]
1. One who, or that which, operates or produces an effect.
2. (Surg.) One who performs some act upon the human body by means of the hand, or with instruments.
3. A dealer in stocks or any commodity for speculative purposes; a speculator. [Brokers’ Cant]
4. (Math.) The symbol that expresses the operation to be performed; — called also facient.

Operatory
Op´er•a•to•ry, n. A laboratory. [Obs.]

Opercle
O´per•cle, n. [Cf.F. opercule. See Operculum.]
1. (Anat.) Any one of the bony plates which support the gill covers of fishes; an opercular bone.
2. (Zoöl.) An operculum.

Operculiferous
O•per•cu•lif´er•ous, a. [ Operculum + -ferous.] (Zoöl.) Bearing an operculum.

Operculiform
O•per´cu•li•form, a. [L. operculum a cover + -form: cf. F. operculiforme.] Having the form of a lid or cover.

Operculigenous
O•per•cu•lig•e•nous, a. [ Operculum + -genous.] (Zoöl.) Producing an operculum; — said of the foot, or part of the foot, of certain mollusks.

Operculum
O•per´cu•lum, n. ; pl. L. Opercula (#), E. Operculums (#). [L., a cover or lid, fr. operire to cover.]
1. (Bot.) (a) The lid of a pitcherform leaf. (b) The lid of the urnlike capsule of mosses.
2. (Anat.) (a) Any lidlike or operculiform process or part; as the opercula of a dental follicle. (b) The fold of integument, usually supported by bony plates, which protects the gills of most fishes and some amphibians; the gill cover; the gill lid. (c) The principal opercular bone in the upper and posterior part of the gill cover.
3. (Zoöl.) (a) The lid closing the aperture of various species of shells, as the common whelk. See Illust. of Gastropoda. (b) Any lid-shaped structure closing the aperture of a tube or shell.

Operose
Op´er•ose a. [L. operosus, fr. opera pains, labor, opus, operis, work, labor.] Wrought with labor; requiring labor; hence, tedious; wearisome. "Operose proceeding." Burke. "A very operose calculation." De Quincey. — Op´er•ose•ly, adv. — Op´er•ose•ness, n.

Operosity
Op•er•os´i•ty, n. [L. operositas.] Laboriousness. [R.] Bp. Hall.

Operous
Op´er•ous, a. Operose. [Obs.] Holder. — Op´er•ous•ly, adv. [Obs.]

Opertaneous
Op•er•ta´ne•ous, a. [L. opertaneus; operire to hide.] Concealed; private. [R.]

Opetide
Ope´tide, n. [ Ope + tide.] Open time; — applied to different things: (a) The early spring, or the time when flowers begin opening. [Archaic] Nares. (b) The time between Epiphany and Ash Wednesday wherein marriages were formerly solemnized publicly in churches. [Eng.] (c) The time after harvest when the common fields are open to all kinds of stock. [Prov.Eng.] Halliwell. [Written also opentide.]

Ophelic
O•phel´ic, a. (Chem.) Of, pertaining to, or designating, a substance (called ophelic acid) extracted from a plant ( Ophelia) of the Gentian family as a bitter yellowish sirup, used in India as a febrifuge and tonic.

Ophicleide
Oph´i•cleide, n. [F. ophicleide, fr. Gr. ’o•fis a serpent +, gen., a key. So named because it was in effect the serpent, an old musical instrument, with keys added.] (Mus.) A large brass wind instrument, formerly used in the orchestra and in military bands, having a loud tone, deep pitch, and a compass of three octaves; — now generally supplanted by bass and contrabass tubas. Moore (Encyc. of Music).

Ophidia
O•phid´i•a, n. pl. [NL., fr. Gr., dim. of ’o•fis a snake.] (Zoöl.) The order of reptiles which includes the serpents. The most important divisions are: the Solenoglypha, having erectile perforated fangs, as the rattlesnake; the Proteroglypha, or elapine serpents, having permanently erect fang, as the cobra; the Asinea, or colubrine serpents, which are destitute of fangs; and the Opoterodonta, or Epanodonta, blindworms, in which the mouth is not dilatable.

Ophidian
O•phid´i•an, n. [Cf. F. ophidien.] (Zoöl.) One of the Ophidia; a snake or serpent.

Ophidian
O•phid´i•an, a. [Cf. F. ophidien.] (Zoöl.) Of or pertaining to the Ophidia; belonging to serpents.

Ophidioid
O•phid´i•oid, a. [ Ophidion + -oid.] (Zoöl.) Of or pertaining to the Ophidiidae, a family of fishes which includes many slender species. — n. One of the Ophidiidae.

Ophidion
O•phid´i•on, n. ; pl. Ophidia (#). [L., fr. Gr. little snake, fr. ’o•fis a serpent.] (Zoöl.) The typical genus of ophidioid fishes. [Written also Ophidium.] See Illust. under Ophidioid.

Ophiolatry
O•phi•ol´a•try, n. [Gr. ’o•fis serpent + worship.] The worship of serpents. { O•phi•o•log´ic, O•phi•o•log´ic•al } a. Of or pertaining to ophiology.

Ophiologist
O•phi•ol´o•gist, n. One versed in the natural history of serpents.

Ophiology
O•phi•ol´o•gy, n. [Gr. ’o•fis a serpent + -logy: cf.F. ophioloqie.] That part of natural history which treats of the ophidians, or serpents.

Ophiomancy
O´phi•o•man•cy, n. [Gr. ’o•fis a serpent + -mancy: cf. F. ophiomantie.] Divination by serpents, as by their manner of eating, or by their coils.

Ophiomorpha
O•phi•o•mor´pha, n. pl. [NL. See Ophiomorphous.] (Zoöl.) An order of tailless amphibians having a slender, wormlike body with regular annulations, and usually with minute scales imbedded in the skin. The limbs are rudimentary or wanting. It includes the caecilians. Called also Gymnophiona and Ophidobatrachia.

Ophiomorphous
O•phi•o•mor´phous, a. [Gr. ’o•fis a serpent + -morphous.] Having the form of a serpent.

Ophiophagous
O•phi•oph´a•gous, a. [Gr. ’o•fis a serpent + fagei^n to eat: cf. F. ophiophage.] (Zoöl.) Feeding on serpents; — said of certain birds and reptiles.

Ophiophagus
O•phi•oph´a•gus, n. [NL. See Ophiophagous.] (Zoöl.) A genus of venomous East Indian snakes, which feed on other snakes. Ophiophagus elaps is said to be the largest and most deadly of poisonous snakes.

Ophite
O´phite, a. [Gr. ’ofi•ths, fr. ’o•fis a serpent.] Of or pertaining to a serpent. [Obs.]

Ophite
O´phite, n. [L. ophites, Gr. ’ofi•ths (sc. ), a kind of marble spotted like a serpent: cf. F. ophite.] (Min.) A greenish spotted porphyry, being a diabase whose pyroxene has been altered to uralite; — first found in the Pyreness. So called from the colored spots which give it a mottled appearance. — O•phi´ic (#), a.

Ophite
O´phite, n. [L. Ophitae, pl. See Ophite, a. ] (Eccl.Hist.) A mamber of a Gnostic serpent-worshiping sect of the second century.

Ophiura
O•phi•u´ra, n. [NL., from Gr. snake + a tail.] (Zoöl.) A genus of ophiurioid starfishes.

Ophiuran
O•phi•u´ran, a. (Zoöl.) Of or pertaining to the Ophiurioidea. — n. One of the Ophiurioidea.

Ophiurid
O•phi•u´rid, n. (Zoöl.) Same as Ophiurioid.

Ophthalmia
Oph•thal´mi•a (of•thal"mi•a), n. [F. ophthalmie, L. ophthalmia, fr. Gr. ’ofqalmi•a, fr. ’ofqalmo•s the eye, akin to E. optic. See Optic.] (Med.) An inflammation of the membranes or coats of the eye or of the eyeball.

Ophthalmological
Oph•thal•mo•log´ic•al, a. Of or pertaining to ophthalmology.

Ophthalmologist
Oph•thal•mol´o•gist, n. One skilled in ophthalmology; an oculist.

Ophthalmology
Oph•thal•mol´o•gy, n. [Gr. ’ofqalmo•s the eye + -logy: cf. F. ophthalmologie.] The science which treats of the structure, functions, and diseases of the eye.

Ophthalmometer
Oph•thal•mom´e•ter, n. [Gr. ’ofqalmo•s eye + -meter.] (Physiol.) An instrument devised by Helmholtz for measuring the size of a reflected image on the convex surface of the cornea and lens of the eye, by which their curvature can be ascertained.

Ophthalmoscope
Oph•thal´mo•scope, n. [From Gr. ’ofqalmo•s the eye + -scope.] (Physiol.) An instrument for viewing the interior of the eye, particularly the retina. Light is thrown into the eye by a mirror (usually concave) and the interior is then examined with or without the aid of a lens. — Oph•thal•mo•scop´ic (#), a.

Ophthalmoscopy
Oph•thal•mos´co•py, n. [Cf. F. ophthalmoscopie.]
1. A branch of physiognomy which deduces the knowledge of a person’s temper and character from the appearance of the eyes.
2. Examination of the eye with the ophthalmoscope.

Ophthalmy
Oph•thal´my, n. Same as Ophthalmia.

Opianyl
O´pi•a•nyl, n. [ Opianic + - yl.] (Chem.) Same as Meconin.

Opiated
O´pi•a•ted, a.
1. Mixed with opiates.
2. Under the influence of opiates.

Opie
O´pie, n. Opium. [Obs.] Chaucer.

Opiferous
O•pif´er•ous, a. [L. opifer; ops, opis, help + ferre to bear.] Bringing help. [R.]

Opifice
Op´i•fice, n. [L. opificium, fr. opifex workman. See Office.] Workmanship. [Obs.] Bailey.

Opinable
O•pin´a•ble, a. [L. opinabilis.] Capable of being opined or thought. Holland.

Opination
Op•i•na´tion, n. [L. opinatio. See Opine,] The act of thinking; a supposition. [Obs.]

Opinator
Op´i•na•tor, n. [L.] One fond of his own opinious; one who holds an opinion. [Obs.] Glanvill.

Opine
O•pine´, v. t. & i. [ imp. & p. p. Opined p. pr. & vb. n. Opining.] [L. opinari, p. p. opinatus; akin to opinus (in comp.) thinking, and perh. to E. apt: cf. F. opiner.] To have an opinion; to judge; to think; to suppose. South.

Opiniated
O•pin´ia•ted, a. Opinionated. [Obs.]

Opiniative
O•pin´ia•tive, a. Opinionative. Glanvill. — O•pin´ia•tive•ly, adv. — O•pin´ia•tive•ness, n. { O•pin•ia´tor, O•pin•ia´tre }, n. One who is opinionated. [Obs.] South. Barrow.

Opiniatre
O•pin•ia´tre, a. See Opiniaster. [Obs.] Locke.

Opinicus
O•pin´i•cus, n. (Her.) An imaginary animal borne as a charge, having wings, an eagle’s head, and a short tail; — sometimes represented without wings.

Opining
O•pin´ing, n. Opinion. [Obs.] Jer. Taylor.

Opinion
O•pin´ion, n. [F., from L. opinio. See Opine.]
1. That which is opined; a notion or conviction founded on probable evidence; belief stronger than impression, less strong than positive knowledge; settled judgment in regard to any point of knowledge or action.
"Opinion is when the assent of the understanding is so far gained by evidence of probability, that it rather inclines to one persussion than to another, yet not without a mixture of incertainty or doubting." Sir M. Hale.
"I can not put off my opinion so easily." Shak.
2. The judgment or sentiment which the mind forms of persons or things; estimation.
"I have bought golden opinions from all sorts of people." Shak.
"Friendship … gives a man a peculiar right and claim to the good opinion of his friend." South.
"However, I have no opinion of those things." Bacon.
3. Favorable estimation; hence, consideration; reputation; fame; public sentiment or esteem. [Obs.]
"Thou hast redeemed thy lost opinion." Shak.
"This gained Agricola much opinion, who … had made such early progress into laborious … enterprises." Milton.
4. Obstinacy in holding to one’s belief or impression; opiniativeness; conceitedness. [Obs.] Shak.
5. (Law.) The formal decision, or expression of views, of a judge, an umpire, a counselor, or other party officially called upon to consider and decide upon a matter or point submitted. To be of opinion, to think; to judge. - - To hold opinion with, to agree with. [Obs.] Shak.
Syn. — Sentiment; notion; persuasion; idea; view; estimation. See Sentiment.

Opinion
O•pin´ion, v. t. To opine. [Obs.]

Opinionable
O•pin´ion•a•ble, a. Being, or capable of being, a matter of opinion; that can be thought; not positively settled; as an opinionable doctrine. C. J. Ellicott.

Opinionate
O•pin´ion•ate, a. Opinionated.

Opinionated
O•pin´ion•a•ted, a. Stiff in opinion; firmly or unduly adhering to one’s own opinion or to preconceived notions; obstinate in opinion. Sir W. Scott.

Opinionately
O•pin´ion•ate•ly, adv. Conceitedly. Feltham.

Opinionatist
O•pin´ion•a•tist, n. An opinionist. [Obs.]

Opinionative
O•pin´ion•a•tive, a.
1. Unduly attached to one’s own opinions; opinionated. Milton.
2. Of the nature of an opinion; conjectured. [Obs.] "Things both opinionative and practical." Bunyan. — O•pin´ion•a•tive•ly, adv. — O•pin´ion•a•tive•ness, n.

Opinionator
O•pin´ion•a•tor, n. An opinionated person; one given to conjecture. [Obs.] South.

Opinioned
O•pin´ioned, a. Opinionated; conceited.
"His opinioned zeal which he thought judicious." Milton.

Opinionist
O•pin´ion•ist, n. [Cf. F. opinioniste.] One fond of his own notions, or unduly attached to his own opinions. Glanvill.

Opiparous
O•pip´a•rous, a. [L. opiparus, fr. ops, opis, riches + parare to provide.] Sumptuous. [Obs.] — O•pip´a•rous•ly, adv. [Obs.] E. Waterhouse.

Opisometer
Op•i•som´e•ter, n. [Gr. backwards + -meter.] An instrument with a revolving wheel for measuring a curved line, as on a map.

Opisthion
O•pis´thi•on, n. [NL., fr. Gr. hinder.] (Anat.) The middle of the posterior, or dorsal, margin of the great foramen of the skull. { O•pis•tho•bran´chi•a, O•pis•tho•bran•chi•a´ta } n. pl. [NL., from Gr. behind + gills.] (Zoöl.) A division of gastropod Mollusca, in which the breathing organs are usually situated behind the heart. It includes the tectibranchs and nudibranchs.

Opisthobranchiate
O•pis•tho•bran´chi•ate, a. (Zoöl.) Of or pertaining to the Opisthobranchiata. — n. One of the Opisthobranchiata. { O•pis•tho•cœ"li•an, O•pis•tho•cœ"lous } a. [Gr. behind + koi^los hollow,] (Anat.) Concave behind; — applied especially to vertebrae in which the anterior end of the centrum is convex and the posterior concave.

Opisthodome
O•pis´tho•dome, n. [L. opisthodomus, Gr. ; behind + do•mos house: cf. F. opisthodome.] (Arch.) A back chamber; especially, that part of the naos, or cella, farthest from the main entrance, sometimes having an entrance of its own, and often used as a treasury.

Opisthoglypha
O•pis•tho•glyph´a, n. pl. [NL., from Gr. behind + to carve.] (Zoöl.) A division of serpents which have some of the posterior maxillary teeth grooved for fangs.

Opisthography
Op•is•thog´ra•phy, n. [Gr. behind + -graphy.] A writing upon the back of anything, as upon the back of a leaf or sheet already written upon on one side. [R.] Scudamore.

Opisthomi
Op•is•tho´mi, n. pl. [NL., fr. Gr. behind + the shoulder.] (Zoöl.) An order of eellike fishes having the scapular arch attached to the vertebrae, but not connected with the skull.

Opisthopulmonate
O•pis•tho•pul´mo•nate, a. [Gr. behind + E. pulmonate.] (Zoöl.) Having the pulmonary sac situated posteriorly; — said of certain air-breathing Mollusca.

Opisthotic
Op•is•thot´ic, n. [Gr. behind +,, ear.] (Anat.) The inferior and posterior of the three elements forming the periotic bone.

Opisthotonos
Op•is•thot´o•nos, n. [NL., from Gr. backwards + a stretching.] (Med.) A tetanic spasm in which the body is bent backwards and stiffened.

Opitulation
O•pit•u•la´tion, n. [L. opitulatio, fr. opitulari to bring help.] The act of helping or aiding; help. [Obs.] Bailey.

Opium
O´pi•um, n. [L., fr. Gr. poppy juice, dim. of vegetable juice.] (Chem.) The inspissated juice of the Papaver somniferum, or white poppy. Opium is obtained from incisions made in the capsules of the plant, and the best flows from the first incision. It is imported into Europe and America chiefly from the Levant, and large quantities are sent to China from India, Persia, and other countries. It is of a brownish yellow color, has a faint smell, and bitter and acrid taste. It is a stimulant narcotic poison, which may produce hallicinations, profound sleep, or death. It is much used in medicine to soothe pain and inflammation, and is smoked as an intoxicant with baneful effects. Opium joint, a low resort of opium smokers. [Slang]

Ople tree
O"ple tree [L. opulus a kind of maple tree.] The witch-hazel. [Obs.] Ainsworth. { Op•o•bal´sam, Op•o•bal´sa•mum } n. [L. opobalsamum, Gr. ; vegetable juice + balsam.] (Med.) The old name of the aromatic resinous juice of the Balsamodendron opobalsamum, now commonly called balm of Gilead. See under Balm.

Opolchenie
Op•ol•che´ni•e, n. [Russ., fr. opolchit’ to make an army, polk army. Cf. Folk.] (Russia) See Army organization, above.

Opossum
O•pos´sum, n. [Of N. American Indian origin.] (Zoöl.) Any American marsupial of the genera Didelphys and Chironectes. The common species of the United States is Didelphys Virginiana. Several related species are found in South America. The water opossum of Brazil ( Chironectes variegatus), which has the hind feet, webbed, is provided with a marsupial pouch and with cheek pouches. It is called also yapock. Opossum mouse. (Zoöl.) See Flying mouse, under Flying. — Opossum shrimp (Zoöl.), any schizopod crustacean of the genus Mysis and allied genera. See Schizopoda.

Oppignerate
Op•pig´ner•ate, v. i. [L. oppigneratus, p. p. of oppignerare to pawn. See Ob-, and Pignerate.] To pledge; to pawn. [Obs.] Bacon.

Oppilative
Op•pi•la•tive, a. [Cf. F. opilatif. See Oppilate.] Obstructive. [Obs.] Sherwood. { Op•plete´, Op•plet´ed } a. [L. oppletus, p. p. of opplere to fill up; ob (see Ob-) + plere to fill.] Filled; crowded. [Obs.] Johnson.

Oppone
Op•pone´, v. t. [L. opponere. See Opponent.] To oppose. [Obs.] B. Jonson.

Opponent
Op•po´nent, a. [L. opponens, -entis, p. pr. of opponere to set or place against, to oppose; ob (see Ob-) + ponere to place. See Position.] Situated in front; opposite; hence, opposing; adverse; antagonistic. Pope.

Opponent
Op•po´nent, n.
1. One who opposes; an adversary; an antagonist; a foe. Macaulay.
2. One who opposes in a disputation, argument, or other verbal controversy; specifically, one who attacks some theirs or proposition, in distinction from the respondent, or defendant, who maintains it.
"How becomingly does Philopolis exercise his office, and seasonably commit the opponent with the respondent, like a long-practiced moderator!" Dr. H. More.
Syn. — Antagonist; opposer; foe. See Adversary.

Opportunism
Op•por•tun´ism, n. [Cf. F. opportunisme.] The art or practice of taking advantage of opportunities or circumstances, or of seeking immediate advantage with little regard for ultimate consequences. [Recent]

Opportunist
Op•por•tun´ist, n. [Cf. F. opportuniste.] One who advocates or practices opportunism. [Recent]

Opportunity
Op•por•tu´ni•ty, n. ; pl. Opportunities (#). [F. opportunite, L. opportunitas. See Opportune.]
1. Fit or convenient time; a time or place favorable for executing a purpose; a suitable combination of conditions; suitable occasion; chance.
"A wise man will make more opportunities than he finds." Bacon.
2. Convenience of situation; fitness. [Obs.]
"Hull, a town of great strength and opportunity, both to sea and land affairs." Milton.
3. Importunity; earnestness. [Obs.] Jer. Taylor.
Syn. — Occasion; convenience; occurrence. — Opportunity, Occasion. An occasion is that which falls in our way, or presents itself in the course of events; an opportunity is a convenience or fitness of time, place, etc., for the doing of a thing. Hence, occasions often make opportunities. The occasion of sickness may give opportunity for reflection.

Opposable
Op•pos´a•ble, a.
1. Capable of being opposed or resisted.
2. Capable of being placed opposite something else; as the thumb is opposable to the forefinger.

Opposal
Op•pos´al, n. Opposition. [R.] Sir T. Herbert.

Oppose
Op•pose´, v. t. [ imp. & p. p. Opposed p. pr. & vb. n. Opposing.] [F. opposer. See Ob-, Pose, and cf.2d Appose, Puzzle, n. Cf.L. opponere, oppositum.]
1. To place in front of, or over against; to set opposite; to exhibit.
"Her grace sat down … In a rich chair of state; opposing freely The beauty of her person to the people." Shak.
2. To put in opposition, with a view to counterbalance or countervail; to set against; to offer antagonistically.
"I may … oppose my single opinion to his." Locke.
3. To resist or antagonize by physical means, or by arguments, etc.; to contend against; to confront; to resist; to withstand; as to oppose the king in battle; to oppose a bill in Congress.
4. To compete with; to strive against; as to oppose a rival for a prize.
"I am … too weak To oppose your cunning." Shak.
Syn. — To combat; withstand; contradict; deny; gainsay; oppugn; contravene; check; obstruct.

Oppose
Op•pose´, v. i.
1. To be set opposite. Shak.
2. To act adversely or in opposition; — with against or to; as a servant opposed against the act. [Obs.] Shak.
3. To make objection or opposition in controversy.

Opposeless
Op•pose´less, a. Not to be effectually opposed; irresistible. [Obs.] "Your great opposeless wills." Shak.

Opposer
Op•pos´er, n. One who opposes; an opponent; an antagonist; an adversary.

Opposite
Op´po•site, a. [F., fr. L. oppositus, p. p. of opponere. See Opponent.]
1. Placed over against; standing or situated over against or in front; facing; — often with to; as a house opposite to the Exchange.
2. Applied to the other of two things which are entirely different; other; as the opposite sex; the opposite extreme.
3. Extremely different; inconsistent; contrary; repugnant; antagonistic.
"Novels, by which the reader is misled into another sort of pieasure opposite to that which is designed in an epic poem." Dryden.
"Particles of speech have divers, and sometimes almost opposite, significations." Locke.
4. (Bot.) (a) Set over against each other, but separated by the whole diameter of the stem, as two leaves at the same node. (b) Placed directly in front of another part or organ, as a stamen which stands before a petal.

Opposite
Op´po•site, n.
1. One who opposes; an opponent; an antagonist. [Obs.]
"The opposites of this day’s strife." Shak.
2. That which is opposed or contrary; as sweetness and its opposite.
"The virtuous man meets with more opposites and opponents than any other." Landor.

Oppositely
Op´po•site•ly, adv. In a situation to face each other; in an opposite manner or direction; adversely.
"Winds from all quarters oppositely blow." May.

Oppositeness
Op´po•site•ness, n. The quality or state of being opposite.

Oppositifolious
Op•pos•i•ti•fo´li•ous, a. [See Opposite, Folious.] (Bot.) Placed at the same node with a leaf, but separated from it by the whole diameter of the stem; as an oppositifolious peduncle.

Oppositipetalous
Op•pos•i•ti•pet´al•ous, a. [See Opposite, and Petal.] (Bot.) Placed in front of a petal.

Oppressive
Op•press´ive, a. [Cf. F. oppressif.]
1. Unreasonably burdensome; unjustly severe, rigorous, or harsh; as oppressive taxes; oppressive exactions of service; an oppressive game law. Macaulay.
2. Using oppression; tyrannical; as oppressive authority or commands.
3. Heavy; overpowering; hard to be borne; as oppressive grief or woe.
"To ease the soul of one oppressive weight." Pope. — Op•press´ive•ly, adv. — Op•press´ive•ness, n.

Oppressor
Op•press´or, n. [L.] One who oppresses; one who imposes unjust burdens on others; one who harasses others with unjust laws or unreasonable severity.
"The orphan pines while the oppressor feeds." Shak.
"To relieve the oppressed and to punish the oppressor." Swift.

Oppressure
Op•pres´sure, n. Oppression. [Obs.]

Opprobrious
Op•pro´bri•ous, a. [L. opprobriosus, fr. opprobrium. See Opprobrium.]
1. Expressive of opprobrium; attaching disgrace; reproachful; scurrilous; as opprobrious language.
"They … vindicate themselves in terms no less opprobrious than those by which they are attacked." Addison.
2. Infamous; despised; rendered hateful; as an opprobrious name.
"This dark, opprobrious den of shame." Milton. — Op•pro´bri•ous•ly, adv. — Op•pro´bri•ous•ness, n.

Oppugn
Op•pugn´, v. t. [ imp. & p. p. Oppugned p pr. & vb. n. Oppugning.] [OF. oppugner, L. oppugnare; ob (see Ob-) + pugnare to fight. See Impugn.] To fight against; to attack; to be in conflict with; to oppose; to resist.
"They said the manner of their impeachment they could not but conceive did oppugn the rights of Parliament." Clarendon.

Oppugner
Op•pugn´er, n. One who opposes or attacks; that which opposes. Selden.

Opsimathy
Op•sim´a•thy, n. [Gr. .] Education late in life. [R.] Hales.

Opsiometer
Op•si•om´e•ter, n. [Gr. sight + -meter: cf. F. opsiomètre.] An instrument for measuring the limits of distincts vision in different individuals, and thus determiming the proper focal length of a lens for correcting imperfect sight. Brande & C.

Opsonation
Op•so•na´tion, n. [L. opsonatio.] A catering; a buying of provisions. [Obs.] Bailey.

Optable
Op´ta•ble, a. [L. optabilis.] That may be chosen; desirable. [Obs.] Cockeram.

Optate
Op´tate, v. i. [L. optatus, p. p. of optare.] To choose; to wish for; to desire. [Obs.] Cotgrave.

Optation
Op•ta´tion, n. [L. optatio. See Option.] The act of optating; a wish. [Obs.] Sir T. Browne.

Optatively
Op´ta•tive•ly, adv. In an optative manner; with the expression of desire. [R.]
"God blesseth man imperatively, and man blesseth God optatively." Bp. Hall.

Optic
Op´tic, n. [From Optic, a. ]
1. The organ of sight; an eye.
"The difference is as great between The optics seeing, as the object seen." Pope.
2. An eyeglass. [Obs.] Herbert. { Op´tic, Op´tic•al } a. [F. optique, Gr. ; akin to sight, I have seen, I shall see, and to the two eyes, face, L. oculus eye. See Ocular, Eye, and cf. Canopy, Ophthalmia.]
1. Of or pertaining to vision or sight.
"The moon, whose orb Through optic glass the Tuscan artist views." Milton.
2. Of or pertaining to the eye; ocular; as the optic nerves (the first pair of cranial nerves) which are distributed to the retina. See Illust. of Brain, and Eye.
3. Relating to the science of optics; as optical works. Optic angle (Opt.), the angle included between the optic axes of the two eyes when directed to the same point; — sometimes called binocular parallax. — Optic axis. (Opt.) (a) A line drawn through the center of the eye perpendicular to its anterior and posterior surfaces. In a normal eye it is in the direction of the optic axis that objects are most distinctly seen. (b) The line in a doubly refracting crystal, in the direction of which no double refraction occurs. A uniaxial crystal has one such line, a biaxial crystal has two. - - Optical circle (Opt.), a graduated circle used for the measurement of angles in optical experiments. — Optical square, a surveyor’s instrument with reflectors for laying off right angles.

Optimates
Op•ti•ma´tes, n. pl. [L. See Optimate.] The nobility or aristocracy of ancient Rome, as opposed to the populares.

Optimism
Op´ti•mism, n. [L. optimus the best; akin to optio choice: cf. F. optimisme. See Option.]
1. (Metaph.) The opinion or doctrine that everything in nature, being the work of God, is ordered for the best, or that the ordering of things in the universe is such as to produce the highest good.
2. A disposition to take the most hopeful view; — opposed to pessimism.

Optimistic
Op•ti•mis´tic, a.
1. (Metaph.) Of or pertaining to optimism; tending, or conforming, to the opinion that all events are ordered for the best.
2. Hopeful; sanguine; as an optimistic view.

Optimity
Op•tim´i•ty, n. [L. optimitas, fr. optimus the best.] The state of being best. [R.] Bailey.

Option
Op´tion, n. [L. optio; akin to optare to choose, wish, optimus best, and perh. to E. apt: cf. F. option.]
1. The power of choosing; the right of choice or election; an alternative.
"There is an option left to the United States of America, whether they will be respectable and prosperous, or contemptible and miserable, as a nation." Washington.
2. The exercise of the power of choice; choice.
"Transplantation must proceed from the option of the people, else it sounds like an exile." Bacon.
3. A wishing; a wish. [Obs.] Bp. Hall.
4. (Ch. of Eng.) A right formerly belonging to an archbishop to select any one dignity or benefice in the gift of a suffragan bishop consecrated or confirmed by him, for bestowal by himself when next vacant; — annulled by Parliament in 1845.
5. (Stock Exchange) A stipulated privilege, given to a party in a time contract, of demanding its fulfillment on any day within a specified limit. Buyer’s option, an option allowed to one who contracts to buy stocks at a certain future date and at a certain price, to demand the delivery of the stock (giving one day’s notice) at any previous time at the market price. — Seller’s option, an option allowed to one who contracts to deliver stock art a certain price on a certain future date, to deliver it (giving one day’s notice) at any previous time at the market price. Such options are privileges for which a consideration is paid. — Local option. See under Local.
Syn. — Choice; preference; selection. — Option, Choice. Choice is an act of choosing; option often means liberty to choose, and implies freedom from constraint in the act of choosing.

Optogram
Op´to•gram, n. [ Optic + - gram: cf. F. optogramme.] (Physiol.) An image of external objects fixed on the retina by the photochemical action of light on the visual purple. See Optography.

Optometrist
Op•tom´e•trist, n. One who is skilled in or practices optometry.

Optometry
Op•tom´e•try, n.
1. (Med.) Measurement of the range of vision, esp. by means of the optometer.
2. As defined (with minor variations) in the statutes of various States of the United States: (a) "The employment of subjective and objective mechanical means to determine the accomodative and refractive states of the eye and the scope of its function in general." (b) "The employment of any means, other than the use of drugs, for the measurement of the powers of vision and adaptation of lenses for the aid thereof."

Opulence
Op´u•lence, n. [L. opulentia: cf. F. opulence. See Opulent.] Wealth; riches; affluence. Swift

Opus
O´pus, n. ; pl. Opera (#). [L. See Opera.] A work; specif. (Mus.), a musical composition. Each composition, or set of pieces, as the composer may choose, is called an opus, and they are numbered in the order of their issue. (Often abbrev. to op.) Opus incertum. [L.] (Arch.) See under Incertum. { O•pus´cle, O•pus´cule } n. [L. opusculum, dim. of opus work: cf. F. opuscule.] A small or petty work.

Opye
O´pye, n. Opium. [Obs.] Chaucer.