I'm a little surprised to be saying this, but Tibby's right.
If you say you cheated on someone, that tells me that you hurt them by doing something they trusted you not to do. It seems a little duplicitous to go looking for a more "precise" definition of cheating ("well, it has to involve at least kissing, and you have to know that you shouldn't be doing it..." &c &c &c): what else can the objective be but to establish your own righteousness in an argument? The point is that your partner's feelings are hurt; gerrymandering definitions isn't going to help anything.
Of course, you can perfectly well ask, "What counts as cheating for us; what are the boundaries of our relationship?" (That is: "What do you expect me not to do?") But asking that question online is more like taking a poll of everyone's favorite ice cream.