For the record I would describe myself is a wife-sharing cock-friendly Stag, not a Cuck.
This is just my opinion on the subject but for many years when referring to my sexual preference I would say I was "Bi". I was using more as a blanket term more than anything else since in certain situations I was in to performing or receiving oral from another man. A few years back that changed, I met a bisexual man and realized that my use of "Bi" was misleading. He "educated" me on what it meant to be a bisexual man and I was no where near his level. Being bisexual had a far more deeper meaning to him than just the sexual component. For this reason I quite referring to myself as Bi an adopted a couple of other terms or alternative labels that I feel were more accurate. One is "cock-friendly" and the other was "bi-friendly".
I agree with Lynnandhubby and that the use of "cuck' is a bit too fluid. Like Stag, being a Cuck does cover some specific behavior unique to the label. I am speaking very generally here but one of the many differences is that as a Stag, humiliation is not part of the experience. Where as a cuckold it is a big part of the role. Of course there may be cross over parts to each which I would consider a nuance to the situations couples experience. In our MFM adventures I have participated in some cases, by getting the other guy hard, sucking on him while he has sex with the wife, and cleaning him afterwards. I don't do this because I am playing a submissive role, I do it because it arouses me sexually. I am not attracted to men but I am in to sucking cock either with or without the wife. A Cock-Friendly Husband.