Since it’s a topic of discussion these days.
Scenario: You’ve just done something physically and/or emotionally intimate with another consenting adult human being who is not your spouse/partner.
So, gonna tell your partner?
b) Any other response.
If the answer is “b,” then there’s a really excellent chance you’re cheating.
“Cheating” is not about whether you’ve physically met someone, whether they’re in the same room with you, the levels of dress you or they are wearing, or whether what you’re doing with them can be quantified on a baseball diamond. Cheating is allowing another person into a level of intimacy your partner expects to be theirs alone. That level of intimacy is not uniform from person to person. There is no guarantee that your partner’s expected level of intimacy will be entirely congenial to you; in that respect what qualifies as “cheating” is not up to you.
Most people get that. Most people also don’t want to hurt their partner and/or don’t want to get caught doing something they know their partner will consider cheating. Which is why any other response than an unqualified “yes” to telling your partner about an intimate encounter with another consenting adult human being is a good first indicator you’ve just done yourself some cheating.
(If you’re having intimate encounters with someone who is not consenting and/or adult and/or a human being, you have other problems as well, which we will not delve into now.)
Note that in my formulation, what anyone else other than your partner thinks is cheating (or not) is immaterial, because those other people are not in the same relationship you are with your partner. Friends/family/workmates/strangers may choose to think you’re a cheating horndog; they may choose to think your partner is being entirely unreasonable about what constitutes “cheating”; they may think you both are idiots. They can have any opinion they want. They can also go fly a kite. In the end, the opinion you need to be concerned about is your partner’s.
If you’re not an idiot (or brand new to the relationship), then you probably should have a good idea what constitutes “cheating” in your relationship. If you don’t know (and aren’t content with being branded an idiot), you should probably ask. It will be a clarifying discussion, if nothing else. If you don’t want to ask, a) you’re an idiot, and b) here’s a tip: if you ever find yourself in a situation where you ask yourself, “this thing I’m doing, it doesn’t really count as cheating, does it?” then the answer is probably “yeah, it does.” Because if you have to ask, etc.