1. ratfink - Noun
2. ratfink - Verb
An informer or spy; a traitor. [from 1960s]
(also attributive) A dislikable or contemptible person. [from 1960s]
ratfink (third-person singular simple present ratfinks, present participle ratfinking, simple past and past participle ratfinked)
(transitive) To inform on; to betray. [from 1970s]