Definition of rat in English:

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Pronunciation: /rat/


1A rodent that resembles a large mouse, typically having a pointed snout and a long, sparsely haired tail. Some kinds have become cosmopolitan and are sometimes responsible for transmitting diseases.
  • Family Muridae: many genera, including Rattus (the Old World rats), and several hundred species.
Example sentences
  • Most people are familiar with mice, rats, hamsters, and guinea pigs, which are commonly kept as pets.
  • Cane rats should not be confused with domestic rodents such as rats and mice which can be disease-carrying vermin.
  • Up until 1987 this kind of experiment had only done in rodents, rats and mice, and in lower organisms.
2 informal A person regarded as despicable, especially a man who has been deceitful or disloyal.
Example sentences
  • He, who's a braggart and a drunk and a rat and a scoundrel, at his death bed, says, I find Christ.
  • How can you make a philandering love cheat, who works his way through a family of sisters, anything but a rogue and a rat?
  • ‘For your information this little rat insulted me’ Debbie huffed sticking her chin up snobbishly.
informal beast, pig, swine, creep, louse, lowlife, scumbag, scumbucket, scuzzball, sleazeball, sleazebag, heel, dog, weasel, ratfink
2.1An informer.
Example sentences
  • It's different when Right Wingers want to crush free speech and create a police state environment of informers and rats in a house of worship.
  • I go by beeper now because there's too many rats [informants] on the street.
  • Mr. Ken told me that the rat was an informant for the enemy.
3 [with adjective] North American informal A person who is associated with or frequents a specified place: you and the rest of the tavern rats will have to find a new hangout LA mall rats
More example sentences
  • There's nowhere else I'd rather be right now - on a trip in South Africa with a good crew and having fun, skating everyday, and doing a real skate rat tour.
  • Mali, while seeming sophisticated, wanders in and out of ghetto rat behavior, especially when it comes to her man, Tad Honeywell.
  • At the first, it was decided to axe three popular characters - love rat doctor Matt Ramsden, his teacher wife Charlie, and shopworker Bobbi Lewis.
4US A pad used to give shape or fullness to a woman’s hair.


(rats) informal
Used to express mild annoyance or irritation.
Example sentences
  • I just came upstairs to check the price of something on eBay (under $10, rats!) and saw the clock.
  • Divisions were actually for sale at Behnke, a nursery local to me and I didn't know it - rats!

verb (rats, ratting, ratted)

[no object]
1 (usually as noun ratting) (Of a person, dog, or cat) hunt or kill rats.
Example sentences
  • In another era, perhaps he and his mates would simply have gone out poaching or ratting, grumbling about bloody women along the way.
  • The Shar Pei still exhibits these herding and ratting instincts.
  • The Giant Schnauzer's original job was ratting.
2 informal Desert one’s party, side, or cause.
Example sentences
  • The Stability Pact was to have kept the currency health, but it became inconvenient for France, which ratted, followed by Germany, France, Italy, Holland, and Greece.
  • Shortly afterwards, getting into his car, he was called by name and, when he turned, was shot through the forehead by a fellow extremist who suspected he had ratted.
  • The other men don't shoot the soldier who ratted, however.
3US Give (hair) shape or fullness with a rat.
Example sentences
  • Her ponytail was ratted and her bangs were sticking up all over while her braids were perfectly fine as they always were.
  • She's got long black hair, ratted and dry, and it hangs down over her shoulders like a fern that hasn't been watered in weeks.
  • There was Stacey in her big girl bra, ratted out hair and adult acne.

Phrasal verbs

rat on (also rat out)

informal Inform on (someone) to a person in a position of authority: I never thought Stash would rat on me men will literally choose death over ratting out another prisoner
More example sentences
  • Words and titles are about to become very important as people figure out which one of Cheney's goons ratted her out.
  • ‘I don't think you should rat her out, but let her know you saw her cheating and that it could get her in a lot of trouble,’ suggests Lindsay.
  • I hadn't planned on ratting Ryan out anyway, but his response had taken me by surprise.
inform on, betray, be unfaithful to, stab in the back
informal tell on, sell down the river, blow the whistle on, squeal on, rat out, finger
1.1Break (an agreement or promise): he accused the government of ratting on an earlier pledge
More example sentences
  • If we believe Gordon's account, as relayed through Robert Peston, Blair ratted on a promise to go by November of last year.
  • He ratted on his promise to take me with him - saying that there would be questions in the parliament if he spent too much money.
  • Whatever the cause, France ratted on his agreement, retaking Brest by force.
break, renege on, go back on, welsh on


Old English ræt, probably of Romance origin; reinforced in Middle English by Old French rat. The verb dates from the early 19th century.

  • The rat has been part of our language since Anglo-Saxon times, but its ultimate origin is not known. It probably goes back to the time when the creature first came to Europe from Asia. The term rat race has been used since the mid 20th century. The image behind this is of rats struggling with each other to move forward in a confined space, rather than of the ordered world of a race track. Sailing ships would traditionally have been infested with rats, which would try to escape en masse from a vessel that was in trouble. This gave rise to rats deserting a sinking ship. A person has been a rat since the 1760s, and 50 or so years later to rat started to mean ‘to desert a cause, become a traitor’ and then ‘to inform on’. Someone who suspects a trick is said to smell a rat—a phrase which in the 18th century is found as part of an elaborate mixed metaphor attributed to an Irish politician, Boyle Roche: ‘Mr Speaker, I smell a rat; I see him forming in the air and darkening the sky; but I'll nip him in the bud.’

Words that rhyme with rat

at, bat, brat, cat, chat, cravat, drat, expat, fat, flat, frat, gat, gnat, hat, hereat, high-hat, howzat, lat, mat, matt, matte, Montserrat, Nat, outsat, pat, pit-a-pat, plait, plat, prat, Rabat, rat-tat, Sadat, sat, scat, Sebat, shabbat, shat, skat, slat, spat, splat, sprat, stat, Surat, tat, that, thereat, tit-for-tat, vat, whereat

For editors and proofreaders

Syllabification: rat

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