Reverse Dictionary: MOON (expose the buttocks)

NOUNS
► B.A. an act of exposing one’s buttocks, esp. from the window of an automobile, as an obscene prank; mooning (Bare Ass) → 1970 US students’ sl.

VERBS
► GAUCHO to moon; to expose the buttocks, usually in the window of a car, as an insult to someone → M20 US sl.
► HANG A B.A. to hang a ‘bare ass’; to moon; to expose the buttocks for shock or insult → 1970 US sl.