bum vs crummy

bum is a noun but crummy is not a noun.

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

As adjectives, bum and crummy are synonyms defined as:

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

bum (noun)	crummy (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

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

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