Cheating is when a partner lies about something or crosses established boundaries, whatever they may be. I have friends of opposite sex, so does he. We tell each other about everything that goes on, how we feel, and what we want. If one of us starts hiding certain activities from another, that's cheating. Prohibiting friendships due to insecurity and/ or immaturity is not optional. I'd never be with someone who doesn't want me to have friends that I chose.

cheating is doing something behind your partners back

Opposite-sex friends: fine, normal and healthy
Flirting outside relationship: fine, fun and spicy
Work-wife: fine, silly harmless fun
Other stuff? Let's discuss.

I would have discussed and reached agreement on all this stuff in the very earliest stages of relationship.

Depends entirely on what agreements you made.

Best rule. If you wouldn't do it with your partner / spouse in the room, then you shouldn't be doing it. Cheating is a very thin line that can get crossed easily.

My definition is:

In a committed relationship where love is defined as affection, attention, compassion, understanding, empathy, respect, fidelity, intellectual, and physical connections and the joining of resources etc. are given and received and a promise is made to be exclusive.

Cheating is the breaking of that promise by giving to another what has already been committed without the understanding and agreement that the "commitment" is dissolved.

Friends and work partners have different definitions as they are platonic relationships. The above definition still applies.

Dishonesty with yourself and your partner.

At work in a health insurance commcenter years ago... I was a work spouse to many ladies. I was the only of the men that sticked around for years. They knew I was harmless. They were known as Hector's wives. They showed me their shoes, dresses, etc. When I left they were Hector's widows... I was honored as a friend among grown ups. Nothing wrong with a "work spouse" unless something else is going on. Those were my friends and I theirs.

My last two serious relationships were open so as I date and meet new guys I’m finding myself in “trouble” sometimes. I’m having to retrain my brain into what is socially acceptable since I’m not looking for another open relationship or piss off my potential future relationship. I also have closer friendships with men vs female. My drinking buddies are dudes.

I don't have a partner but I liked the post because it's a good question.

Kind of experiencing something of this now. I told the lady I've been seeing that "I don't get jealous - that if there's another man she prefers to be with - I just get gone". She has an old friend she has known for years (who seems now to be the primary reason her other relationships have failed) and she has such a committed sense of loyalty to this old guy - (15 years our senior) - she puts him before "us" - coffee every Saturday morning and wine every Wednesday. She's known him for longer than she's known me - I get that - and he certainly didn't seem like a threat to me at the time - however, I think he may have an agenda and is giving her bad relationship advice. Starting to perceive it as cheating now. He has encouraged her to "take a break for about a month - just to see if there's anything really there". She's following his advice. What're your thoughts?

Depends on them, I don’t do double standards.

It's all cool as long as I'm in the room. Wait which group is this?

Any sexual conduct sneaking away on a secret deceptive randevu with some else.

In general, jealousy is more about you than the other person.

If my partner is having sex with someone else, then they’re not my partner.
Emotional, I’m not sure. I’m very jealous. So, probably.

Any relationship outside the main relationship that involves lying. If you're not doing anything wrong, there's no reason to lie.

I have a conflict of interest, so I'm sitting out.

I play my cards on a computer, impossible to cheat!

Nothing, anymore. I used to consider a lot of things cheating, but I've been worn down over the years and lack the care for the fight. It's their body, their brain, the actions my significant other takes are the actions that make them happy.
I have a code of morality that wouldn't allow me to cheat, but I'm not actively going to force my perspectives on someone else or get upset at someone for not living up to the standard I've built for myself. I'm not them.