In adult film jargon, “M” refers to masochism (enjoying receiving pain or psychological submission), while “top” usually means the person who initiates or controls the action. On the surface, those seem contradictory. An M man top is a partner who leads the scene but gets pleasure from the woman’s dominance — her verbal teasing, physical edge, or emotional control. He may be on top physically, but psychologically, she’s running the show.