bum vs dirty dog

bum and dirty dog both are nouns.

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

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

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

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

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

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

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