definately a person-- unless the person using the word was english- then anatomy..

and it's used in a lot of idioms-- "give a bum's rush" (to treat a person the same way you might treat a bum)

and bum'ed out-- to be as poor as bum, or as sad as one.

and i would distinguish a bum as being a local drunk, a down and out person , and a hobo as being a transient.. so "i see the same old bums every morning, sleeping in the railroad station".. (actualy, the have all been forced into out of sight places, and i never see the same old bums-- some of whom i had gotten to know by name)