The act of gathering up some friends of yours to hide in a closet in ninja costumes and then while in the same room fuck your girlfriend/boyfriend that you found cheating on you. Make sure its a painfull experience for the other person of course and while in the sex make a key word for the friends to come out of the closet and beat the shit out of the girl or boy. Then have them run off.
Shirly why are you all beaten up?!
I was had by the closet ninjas.