rotter vs dirty dog

rotter and dirty dog both are nouns.

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

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

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

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

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