Hatch Back
(From March 6, 2006)
Definition:
Adjective. The condition where a person is missing his or her gluteus maximus; the image resembles a person's back simply splitting at the bottom into two legs, as though the rump had been sliced off with a sharp object, such as a hatchet.

Used in a sentence:
RICK: Is it me, or does Paris Hilton have no ass?
STEVE: No, she doesn't. She has a hatch back.