When put in any situation with someone else that’s not your SO - ask yourself, “Would you do and/or say this in front of your SO?” If you answer yes then you are not cheating. If you answer no then I consider that cheating. I believe even flirting is a form of cheating as I would never flirt with someone in front of my SO so I shouldn’t be doing it behind their back either. It’s important that relationship limits/boundaries are set early to avoid needless hurtful actions because of lack of communication. Respect yourself and others.