A person who looks and behaves like a completely normal person and is typically not physically imposing, that actually has profound skill in the martial arts without anyone knowing of it.
So I was walking home sort of late last night with Dan when four guys jumped us! While I was cowering on the ground I heard Dan make some Asian noises and a bunch of thuds in quick succession. Then there was silence for a few seconds followed by the sound four bodies hitting the ground. It turns out my brother Dan is a closet ninja.
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.