Msub
Male sub or male submissive/ male submission.

A male who likes to submit to their significant other or dom.

Basically a man who likes being owned or just all in all controlled or dominated. A male finds pleasure in letting the other person do what the feel like to them. This can involve things as pegging, bdsm, or other kinks.
Person 1 - “are you an msub?”

Person 2 - “yeah, I like getting fucked or owned by my s / o”

Person 1 - “oh damn”