The noun rat has 5 senses (first 1 from tagged texts)
1. (5) rat -- (any of various long-tailed rodents similar to but larger than a mouse)
2. scab, strikebreaker, blackleg, rat -- (someone who works (or provides workers) during a strike)
3. 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. informer, betrayer, rat, squealer, blabber -- (one who reveals confidential information in return for money)
5. rat -- (a pad (usually made of hair) worn as part of a woman's coiffure)
Overview of verb rat
The verb rat has 6 senses (no senses from tagged texts)
1. rat -- (desert one's party or group of friends, for example, for one's personal advantage)
2. rat -- (employ scabs or strike breakers in)
3. fink, scab, rat, blackleg -- (take the place of work of someone on strike)
4. rat -- (give (hair) the appearance of being fuller by using a rat)
5. rat -- (catch rats, especially with dogs)
6. 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")