Possible solution if you lose your dictionary
In the past, it seems that there have been users (like me) who have accidentally lost their free Random House dictionary for the eBookwise, and the future looked bleak and evil. Well, the excellent folks at eBookwise Support have just nursed me through mine own disappearance scare, and I am writing up the solution that fixed the lexicographical lunacy (okay, okay, alliteration mode off).
Apparently, you can hide the books in your bookshelf, and even more surprisingly, you can do it accidentally (like I did). Your dictionary just might be lurking in this hidden void. To bring it back, connect your eBookwise to the Internet as usual and go to your Online Bookshelf. With your stylus, click on the bookshelf graphic at the top of the screen (it's right above the two tabs that say "eBookshelf" and "Online Bookshelf"). This will open up a new menu that lets you sort your bookshelf. At the bottom of the menu, there will be a button that either says "show hidden books" or "hide hidden books." Hopefully, it's the former. If so, click "show hidden books," and with any luck, the dictionary will reappear on your Online Bookshelf (under "General Interest"), whence you can now download it. It worked for me.