cheap vs bum

cheap is not a noun while bum is a noun.

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

As adjectives, cheap and bum are synonyms defined as:

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

cheap (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

cheap (adjective)	bum (adjective)
relatively low in price or charging low prices	of very poor quality; flimsy
of very poor quality; flimsy
embarrassingly stingy
tastelessly showy

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