crummy vs bum

crummy is not a noun while bum is a noun.

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

As adjectives, crummy and bum are synonyms defined as:

Other synonyms of crummy include cheap, cheesy, chintzy, punk, sleazy, tinny.

crummy (noun)	bum (noun)
	the fleshy part of the human body that you sit on
	a vagrant
	a person who is deemed to be despicable or contemptible
	person who does no work

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

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