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1. slang A despicable, contemptible, and untrustworthy person. Her ex-husband turned out to be a real rat. I'm so glad she divorced him when she did.
2. slang Someone who provides confidential and damaging information to another person or group; an informant. The boss thinks we've got a rat in our ranks telling the police about our movements.
3. slang Someone who spends an inordinate amount of time at some particular recreational location. Used in combinations. I turned into a real gym rat during college. I go pretty much every day now. She has always been a rink rat, ever since she was a kid, so it's no surprise to me that she ended up playing ice hockey professionally.
4. slang Someone who continues working or is brought in to work during a strike; a scab. The company hired a bunch of rats from out of state to work the mines while we were on strike. After he crossed the picket line in '78, Tom was labeled a rat among his coworkers for the rest of his career.


An exclamation of frustration, disappointment, or vexation. Oh, rats—I dropped another screw. A: "Sorry, I won't be able to come this Saturday." B: "Rats! OK, we'll try to get together some other time."
See also: rat
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.


exclam. Oh, damn! Rats! I broke a nail!
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.
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References in classic literature ?
"Yes, it is infested with rats," said Tabitha tearfully, "I caught seven young ones out of one hole in the back kitchen, and we had them for dinner last Saturday.
"The rats get upon my nerves, Cousin Ribby," said Tabitha.
"Trained rats!" Manuel Fonseca, the contortionist, exploded in the bar-room of the Hotel Annandale, after refusing to drink with Duckworth.
Out of thirty rats there were seven dead,--starved to death.
"And you have heard that rats always leave a sinking ship?"
And one big black rat, who seemed to want to say something to the Doctor, now crept forward timidly along the rail, watching the dog out of the corner of his eye.
And when you throw at a rat or anything, hitch yourself up a tiptoe and fetch your hand up over your head as awkward as you can, and miss your rat about six or seven foot.
Nothing could be extracted from them on cross-examination except that there might have been rats in the house, though they were not aware of it.
On the second occasion she said it was required by the cook for ridding the lower part of the house of rats.
No tale of horror is complete without the rats. In stories of ghosts and murderers they scamper through the echoing rooms, and the gnawing of their teeth is heard behind the wainscot, and their gleaming eyes peer through the holes in the worm-eaten tapestry, and they scream in shrill, unearthly notes in the dead of night, while the moaning wind sweeps, sobbing, round the ruined turret towers, and passes wailing like a woman through the chambers bare and tenantless.
I love to read tales about rats. They make my flesh creep so.
At the same time there came from a workshop across a little yard outside the window, a regular sound of hammering that kept a kind of tune: RAT - tat-tat, RAT - tat-tat, RAT - tat-tat, without any variation.
Presently one of them, a little, mean-faced, black-bearded fellow with a countenance which reminded Tarzan of Pamba, the rat, laid his hand upon the shoulder of a giant who stood next him, and with whom all the others had been arguing and quarreling.
Even if I be likened to a rat, I do not care, provided that that particular rat be wanted by you, and be of use in the world, and be retained in its position, and receive its reward.
'Have you a passport?' asked the rat. 'Out with your passport!'