Also rather vague. Penetrating what with what? When I replace the stopper in a wine bottle, I have penetrated the wine bottle with the stopper, ergo I have cheated??
What if you live in a society where bigamy is legal, is sex with your second wife, "cheating" on your first wife?
What if you're not married but engaged. Is sex with someone other than your fiancé(e) cheating. What if your just "going steady" or just dating regularly?
Would a married man having sex with another man be cheating on his wife? What about sex with an animal or with himself (i.e. masturbation)?
Are there ways of cheating on a spouse that do not even involve sex in any way? (E.g. Not allowing you wife out of the house unless with you. Spending money that, as a couple you have agreed not to spend. A man going out with the "guys" to play poker, or to bowl, leaving the wife alone. A man going rock climbing - or some other non-sexual activity - with another woman. Having a close (intimate but non-sexual) friend of the opposite sex.)
If cheating only is sexual, why is that? If neither you or your spouse want to cook, it seems perfectly OK to always go out to eat or to hire a cook. Same for yard work, house work, medical help, etc., etc. But we apparently don't have that freedom with sex. If one partner does not want sex and the other does, they are not allowed to "hire" it done because that would be "cheating". Why is that the one category of our lives relegated to such exacting standards when the other aspects are not?
I always did have a questioning mind.