When a couple is: Broken up, filed for divorce, separated, and/or otherwise not together, at all. (Even if legally still married, if the they both intend to end the marriage.)
Is sleeping with, dating, kissing, etc someone else considered "cheating"?
ETA: This is not specifically for, about, to, etc anyone or any story I have heard. It's just a question of your opinion. I do understand there are laws in certain areas that dictate otherwise what legal cheating is or is not.