also: ぎりまん
noun
obligation sex
Slang term for sexual intercourse that a woman engages in out of a sense of duty or obligation rather than personal desire. Often used in discussions of relationship dynamics.
彼女は義理マンで応じただけだった。
She only went along with it out of obligation sex.
義理マンなんて、本当の愛情じゃないよ。
Obligation sex isn't real affection, you know.
義理チョコ refers to obligatory chocolate given on Valentine's Day, while 義理マン refers to obligatory sexual intercourse.
Compound of 義理 (giri, 'obligation') and マン (man), a slang abbreviation of マンコ (manko, 'vagina'). The term likely emerged in informal, often male-oriented discourse to describe sex motivated by duty rather than desire.