bum vs drifter

bum and drifter both are nouns.

Word	Noun	Adjective	Verb	Adverb
bum	Yes	Yes	Yes	No
drifter	Yes	No	No	No

As nouns, drifter is a hypernym of bum; that is, drifter is a word with a broader meaning than bum:

bum: a vagrant
drifter: a wanderer who has no established residence or visible means of support

Other hypernyms of bum include clochard, floater, vagabond, vagrant.

bum (noun)	drifter (noun)
the fleshy part of the human body that you sit on	a wanderer who has no established residence or visible means of support
a vagrant
a person who is deemed to be despicable or contemptible
person who does no work

bum (adjective)	drifter (adjective)
of very poor quality; flimsy

bum (verb)	drifter (verb)
ask for and get free; be a parasite
be lazy or idle