Many things consider cheating varies with the partner.

To some people flirting is cheating, to some people sleeping at the opposite sex house even if in separate rooms is cheating, calling someone constantly without engaging in sex is cheating, going on outings with the opposite sex is cheating, and many different things.

It boils down to the partner in the relationship what they consider cheating. But I am sure for most people having sexual intercourse and MouthAction is cheating!