bum / bəm/ inf. • n. 1. a vagrant. ∎  a lazy or worthless person: you ungrateful bum.2. [in comb.] a person who devotes a great deal of time to a specified activity: a ski bum a poker bum.• v. (bummed, bum·ming) 1. [intr.] travel, with no particular purpose or destination: he bummed around Florida for a few months. ∎  pass one's time idly: we spent most of the summer just bumming around.2. [tr.] get by asking or begging: they tried to bum money off us.3. [tr.] make (someone) feel upset or disappointed: it really bummed me out when he forgot my birthday. • adj. of poor quality; bad or wrong: not one bum note was played.PHRASES: give someone (or get) the bum's rush forcibly eject someone (or be forcibly ejected) from a place or gathering. ∎  abruptly dismiss someone (or be abruptly dismissed) for a poor idea or performance.bum² • n. Brit., inf. buttocks.

bum fundament, buttocks. XIV. ME. bom, of unkn. orig.
Hence bum-bailiff XVII.