1. (noun)rat any of various long-tailed rodents similar to but larger than a mouse
2. (noun)scab, strikebreaker, blackleg, rat someone who works (or provides workers) during a strike
3. (noun)rotter, dirty dog, rat, skunk, stinker, stinkpot, bum, puke, crumb, lowlife, scum bag, so-and-so, git a person who is deemed to be despicable or contemptible "only a rotter would do that"; "kill the rat"; "throw the bum out"; "you cowardly little pukes!"; "the British call a contemptible person a `git'"
4. (noun)informer, betrayer, rat, squealer, blabber one who reveals confidential information in return for money
5. (noun)rat a pad (usually made of hair) worn as part of a woman's coiffure
11. (verb)denounce, tell on, betray, give away, rat, grass, shit, shop, snitch, stag give away information about somebody "He told on his classmate who had cheated on the exam"