What is Billy Bum?

a gross guy with a large derrière. most often in the shape of a watermellon

friend: eww look at HIM!
me: yeah i know * gagging noise* total billy bum

Billy Bum - video

Billy Bum; a bum named Billy. Equivalent of a human skid mark. Plural: Bums of Billies

Ratchet ass ho: Ayy yo Billy! Billy Bum! Suck my dick real quicks!