If you can't do it around him/her (your mate) without them getting mad, its cheating.
Sidenote: If he/she acts like he/she isn't worried about YOU cheating on them (or never asks if you are), they're probably cheating on you.
cheating is emotional intent. i ride with jesus man, therefore if you think it you might as well goon and do it. and 9 times out of ten im going to know what youre thinking and i'll get ****.
I think cheating is really psychological. If u begin to lust after someone, even if its in your head, u've commited adultery. Therefore, if u are in a strip club getting a lap dance, for that moment u are desiring someone else other than the person u are commited. With that act of lust, u have cheated on ur girl/man.