n., v., & adj. US sl.
n. a habitual loafer or tramp; a lazy dissolute person.
v. (bummed, bumming) 1 intr. (often foll. by about, around) loaf or wander around; be a bum. 2 tr. get by begging; cadge.
attrib.adj. of poor quality. bum rap imprisonment on a false charge. bum's rush forcible ejection. bum steer false information. on the bum vagrant, begging.
[ prob. abbr. or back-form. f. BUMMER ]