Not intending to be pedantic, if she fucks another guy, you are, by definition, a cuckold. Look it up in a traditional dictionary (vs the made-up Urban Dictionary). Within the "lifestyle" we define ourselves more liberally.
These are my definitions but I think they ring true for most...
- A cuck generally refers to a guy that is submissive to the wife and her needs. Some cucks are considered sissies as they tend to take on a much more feminized role, sometimes dressing in female attire, almost always sucking, cleaning up both wife and bull, sometimes providing another hole.
- A hotwife is a wife who sport fucks with the knowledge and consent of her husband. She may do it without telling him when she does it but he knows she is going to fuck and is good with it.
- A stag is a cuckold (remember, if she fucks others, he's a cuckold by definition) but who isn't into the submissive aspects. His partner is usually considered a vixen and they work together as a team, planning and enjoying her adventures. This is probably the relationship most in line with a traditional marriage, with the added benefit that she gets laid outside the marriage and they both get to enjoy the experience. Some stags don't engage in any male - male contact and don't come in contact with the bulls semen except to claim sloppy seconds. Others are fine with male - male (think heteroflexible) and may suck or do clean up duties but on their terms, not because they are being told to do it. Just from what I've read here, I think a large number of stags actually are on the heteroflexible side, confident in themselves and not concerned with societal conventions.
- Bull - the man that is not her husband that has sex with the married wife. Some, like @Lynnandhubby further define the bull as their primary, the guy for which they will do anything asked. Contrast that with just your average fuck the wife plays with but there is not special connection.
Every guy on this site whose wife has ever fucked another is a cuckold. The only guys here that aren't cuckolds are the guys whose wives haven't or won't fuck others (despite their desires) and single bulls or bulls whose wives don't play. If they do play, than the bull is a bull when he fucks your wife but a cuck (stag, cuck, sissy, whatever) when his wife fucks someone else. I am/have been both a bull and a stag.
As I said, these are my definitions that I have developed from years of observation. Ultimately though, we each define this experience for ourselves and there is no right or wrong, just what floats your boat.
And I agree with
@JaknSuz. If you don't want to fall into the submissive cuckold roll, I suggest you best figure out the ground rules for her sport fucking before she does it.
Has she had another man since you have been together? If not, be prepared for a real gut punch once she does. It is the most intensely erotic experience I've ever had but it's not for everyone. A lot of guys can't handle their wife/gf getting it from another guy, even if they think that's what they want.