I say more important than your definition is how you feel about it.
I consider that I am fairly forgiving, as I try operate on the premise that people are not perfect and it is natural to find other people attractive… then make a mistake.
This attitude has got me in trouble more than once, not because of any act, but because girlfriends have taken offence at my attitude being too relaxed. Apparently, they were looking for someone jealous and protective. I can sympathise with that.
Of course, this attitude again got me into trouble when a girlfriend cheated on me. I forgave her, and she spent the next two months treating me like shit before finally dumping me.
I guess looking at this, there’s not a real lot to recommend my view point, but I keep stumbling on.
If I was to define cheating, I believe that “thinking” is cheating, albeit hard to draw empiricals. If you have no regard for your partner, and you wish to cheat on them, that’s as good as cheating. The spirit in which you act is what I base my (utilitarian) morals on.
Chatting on MSN, flirting using Morse code… the medium doesn’t matter. I’m sure anyone would regard the cheating over the phone the same as face-to-face… so why would this not apply newer media?
Only Puritans other misinterpreters of Judeo-Christian doctrine would regard masturbation as cheating.