dirty dog vs bum

dirty dog and bum both are nouns.

Word	Noun	Adjective	Verb	Adverb
dirty dog	Yes	No	No	No
bum	Yes	Yes	Yes	No

As nouns, dirty dog and bum are synonyms defined as:

dirty dog and bum: a person who is deemed to be despicable or contemptible

Other synonyms of dirty dog include crumb, git, lowlife, puke, rat, rotter, scum bag, scumbag, skunk, so-and-so, stinker, stinkpot.

dirty dog (noun)	bum (noun)
a person who is deemed to be despicable or contemptible	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

dirty dog (adjective)	bum (adjective)
	of very poor quality; flimsy

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