(sex) cuckolding someone

to have sex with (someone else's spouse or lover); to be in cahoots with (an adulterous, cuckolding or cheating person)

cuckoldry: the state of being cheated on by one's own spouse or lover; the state of being subjected to adultery or cheating

oneself / first-person pronoun: I, me (often shows the speaker's lower position in a hierarchy than the addressee) / (Kansai) you

he / distal demonstrative, something far off removed from both speaker and listener: that / boyfriend

distal demonstrative, something far off removed from both speaker and listener: that, yon / particularly, male personal third person pronoun: he / by extension from he: boyfriend

he; boyfriend

(humble, only refers to one's own) a wife (married woman)

spouse

a side dish / a tangent, a digression, something to the side of the main thing