A ninja warrior who, quite literally, kicks ass. They aim straight for the buttocks and pummel mercilessly. See also: 'munkfuck

An elite group of ninjas that discretely enters homes and rapes the shit out of whatever is living in them.

Also, Ass Ninjas are a threat used by parents, telling their children that if they don't go to sleep Ass Ninjas will get them.

a practitioner of the ancient art of ninjitsu, who happens to enjoy smoking the occasional wiener.

gay guy who likes anal