Definition of rat in English:



  • 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.

    • ‘The number of genetic differences between humans and chimps is ten times smaller than that between mice and rats.’
    • ‘Adult male albino rats were housed in the controlled temperature and photoperiod.’
    • ‘He notes that wild cats may have been drawn to settlements where grain stores attracted rats and mice.’
    • ‘Admittedly some of the rodents that possess the ability, such as rats and mice, are almost completely nocturnal.’
    • ‘Control lung tissue was also obtained from adult male rats.’
    • ‘What's the difference between a water vole and a rat?’
    • ‘We used 18 male adult hooded rats that were maintained under the same conditions as those in Experiment 1.’
    • ‘One resident said she has seen rats scurrying out to snatch discarded pieces of bread in broad daylight.’
    • ‘Cane rats should not be confused with domestic rodents such as rats and mice which can be disease-carrying vermin.’
    • ‘Luckily we didn't see any dead rats.’
    • ‘One rat's nest can turn into a colony of 50 rats in six months.’
    • ‘Despite the situation, they're not lab rats in a cage; they're fellow human beings.’
    • ‘Most people are familiar with mice, rats, hamsters, and guinea pigs, which are commonly kept as pets.’
    • ‘Wistar albino rats were divided into five groups.’
    • ‘Pigeons cooed from the rooftops of buildings, and rats scurried along the floor.’
    • ‘It turns out that mice and rats and some other rodents have hearing which looks very similar to ours.’
    • ‘Bodies start to smell like dead rats if you leave them in one place too long.’
    • ‘Inside his Manhattan brownstone lurks something even more terrifying than his business associates: a giant sewer rat.’
    • ‘In one study, researchers exposed laboratory rats to a toxin that is known to cause Parkinson's disease.’
    • ‘Up until 1987 this kind of experiment had only done in rodents, rats and mice, and in lower organisms.’
  • 2informal A person regarded as despicable, especially a man who has been deceitful or disloyal.

    • ‘She's doing it all for her own self pleasure, that rat!’
    • ‘Here was the building that housed the penthouse where Nick had lived, and where she'd met his street rat friend that actually caught her heart for a time.’
    • ‘He, who's a braggart and a drunk and a rat and a scoundrel, at his death bed, says, I find Christ.’
    • ‘You know every rat, snitch and scoundrel on this island, and between them they know everything shady that transpires.’
    • ‘How can you make a philandering love cheat, who works his way through a family of sisters, anything but a rogue and a rat?’
    • ‘Even Thatcher herself wouldn't have dreamed that the king rat builders would so effectively take over an entire country's development with no real opposition.’
    • ‘Most especially, every jerk bureaucrat and greedy welfare rat (particularly the rich ones) with a hand in the public till gets to vote.’
    • ‘I spat at him, ‘I hope your wife finds out what a cheating, lying rat you really are and you get all that you deserve!’’
    • ‘‘For your information this little rat insulted me’ Debbie huffed sticking her chin up snobbishly.’
    • ‘We went back to the set and I watched the Falcon escape from bondage and alert the cops to where the crime boss and his rats were hiding out.’
    • ‘He was so unworthy, a lowly thief, a rat, unfit to breathe Her Majesty's air.’
    • ‘Pretty soon, the hooligans, graffiti artists, drug addicts, pushers - and rats - take over.’
    • ‘Congratulations to Bob, you rat, despite not, building in A01 and NMRing three times.’
    • ‘If you're out there you rat, I finally caught on and I want my money back.’
    • ‘He then recognised the ship approaching them ‘I should've known that rat would be here.’’
    • ‘The good news is that his adviser, that rat Fred Tough, has had to go with him.’
    scoundrel, wretch, rogue
    View synonyms
    1. 2.1An informer.
      • ‘I go by beeper now because there's too many rats [informants] on the street.’
      • ‘He was supposedly the rat who betrayed the Gibraltar Three, the Eksund gun runners and the IRA men assassinated at Loughgall.’
      • ‘Nadeau, as his name would indicate, has no love for informants and rejects the notion that he was a rat.’
      • ‘I would ask you again whether the killing of a rat is murder?’
      • ‘Mr. Ken told me that the rat was an informant for the enemy.’
      • ‘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.’
      • ‘It is funny to see that the rats at various British intelligence agencies are already trying to avoid the blame for the lies told to the British people by Blair.’
      • ‘She may not be a barracks rat, but she's not too far off.’
      • ‘These rats do whistle an alarm, but we didn't hear it.’
      informer, betrayer, stool pigeon
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  • 3North American informal [with adjective] 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’
    • ‘At the first, it was decided to axe three popular characters - love rat doctor Matt Ramsden, his teacher wife Charlie, and shopworker Bobbi Lewis.’
    • ‘Cardboard cutouts of the love rat MP are proliferating.’
    • ‘I'm a 46-year-old Ohio river rat who's gone there half a dozen times to mountain bike and ski.’
    • ‘He fought a handful of amateur and charity fights, earning him some credit as a middle-aged gym rat.’
    • ‘And the bag boys all seem to be happy, happy surf rats, with funny haircuts and pretty smiles.’
    • ‘THERE ARE DOZENS OF dilemmas facing the average gym rat every time he steps foot in the weight room.’
    • ‘I'm the one who always has to get out front and say ‘no’, and explain, and be the lousy wharf rat because they think I'm running a fraud.’
    • ‘The strike taught these wharf rats about power - that working people could get it, and wield it with devastating effect, if they understood that the world depended on them.’
    • ‘Rhyming, however, is the favourite sound effect of slang, as in boob tube television, frat rat member of a US college fraternity.’
    • ‘Then or course there's the biggest closet rat of all, me.’
    • ‘You had your hardcore kids, punks, and skate rats big on yelling and beer, skeptical of synths and Englishmen.’
    • ‘After spending a long, hard winter as a gym rat shut-in, you're probably hot to trot outdoors.’
    • ‘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.’
    • ‘I believe in spirits - I think we all do - and I don't think this woman who lived in this house was too happy when skate rats all showed up to ride her pool.’
    • ‘Contrary to popular opinion, in general they are not just attracting low lifes, low-end demographic users, gym rats and the like.’
    • ‘Too many effective leaders have behaved badly in their love lives to make credible the claim that being a love rat is incompatible with being a good president.’
    • ‘Mali, while seeming sophisticated, wanders in and out of ghetto rat behavior, especially when it comes to her man, Tad Honeywell.’
    • ‘Some eighteen year old street rat from Paris, France… I wanted him so badly in my world of glitz and glamour… what am I saying?’
    • ‘Shouldn't we at least insist she sells some records like, this decade, before she gets any more coverage for her sex romp/love rat lifestyle?’
    • ‘Peralta ripping in back of Mar Vista Elementary School - the first playground he was officially kicked out of as a young skate rat.’
    • ‘The promo challenges non-gym rats to get in shape during a 30-day period.’
    • ‘Gym rats from the east to the west coast prefer tank tops because they allow for complete range of motion and allow gym buffs to admire their flexed muscles at all times.’
    • ‘That bum sitting on a heating grate, smelling like a wharf rat?’
  • 4US A pad used to give shape or fullness to a woman's hair.


  • Used to express mild annoyance or irritation.

    • ‘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!’
    damn, damnation, blast, hell, heck, gordon bennett
    drat, sugar, botheration, flip, flipping heck, flipping hell
    dash, blooming heck, blooming hell, blinking heck, blinking hell
    doggone it, shucks, shoot, tarnation
    confound it, pish
    View synonyms


  • 1(of a person, dog, or cat) hunt or kill rats.

    • ‘The Border is a hunter, earth dog, show dog and obedience dog, a whiz at agility trials, ratting in the barns and tracking.’
    • ‘We reckon the dog might be a bit handy at ratting or hare coursing.’
    • ‘The Shar Pei still exhibits these herding and ratting instincts.’
    • ‘The Giant Schnauzer's original job was ratting.’
    • ‘In another era, perhaps he and his mates would simply have gone out poaching or ratting, grumbling about bloody women along the way.’
    • ‘The dog is immensely pleased with herself; she is heavily pregnant and ratting was evidently a highly desirable break in just sitting in a corner of the kitchen day after day inflating and waiting for the puppies.’
  • 2informal Desert one's party, side, or cause.

    • ‘Ratting on your mates is regarded as a sin in Australia, but if your mates have done the wrong thing and the ratting merely comprises a truthful public disclosure of some relevant information, then it should be encouraged.’
    • ‘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.’
    • ‘And it's equally unsurprising that he would deny it when one of those Liberal insiders ratted and went public.’
    • ‘Yeah, I'll bet she's just the type to rat, eh, Eddie?’
    • ‘Unfortunately, after republicans ratted and robbed and killed and the two governments failed to punish them with more than the odd ‘tut, tut’ unionists decided they'd been sold a pup.’
    • ‘That's especially true if the White House really did call six or more reporters with this leak, since that means that if the names come out there's no way of knowing which reporter ratted.’
    • ‘He always said that he wouldn't tell on me but he always ended up ratting.’
    • ‘The other men don't shoot the soldier who ratted, however.’
    • ‘Anna hit me in the arm a little mad that I had ratted so easily.’
    • ‘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.’
    • ‘Here's an interesting one about sneaky civil servants using their access to databases to rat to the press on Lotto winners.’
    • ‘Talk of Bob Sercombe ratting is just that, his self-preservation demands him staying where he is.’
  • 3US Give (hair) shape or fullness with a rat.

    • ‘Why does a girl like Gwynie have to go and rat up her hair like that?’
    • ‘There was Stacey in her big girl bra, ratted out hair and adult acne.’
    • ‘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.’
    • ‘All he knew was the sad grey eyes of the man, and his long ratted graying hair.’
    • ‘Her ponytail was ratted and her bangs were sticking up all over while her braids were perfectly fine as they always were.’

Phrasal Verbs

  • rat on (also rat out)

    • 1Inform 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’
      • ‘‘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.’
      • ‘The last thing that I need is Zach ratting me out to my parents.’
      • ‘It would perhaps be different if the only two alternatives were ratting him out or deceiving her employer.’
      • ‘Words and titles are about to become very important as people figure out which one of Cheney's goons ratted her out.’
      • ‘I hadn't planned on ratting Ryan out anyway, but his response had taken me by surprise.’
      • ‘He believes (correctly, as it turns out) that a fellow officer has been ratting him out to the precinct's captain.’
      • ‘‘Thanks,’ I said once we were out of the office, ‘for not ratting me out.’’
      • ‘You ever considered ratting her out to your parents?’
      • ‘Christy was going to pay dearly for ratting her out.’
      • ‘I like her and she lets me get out of class when I need to without ratting me out.’
      inform against, inform on, betray, be disloyal to, be unfaithful to, break one's promise to, break faith with, sell out, stab someone in the back
      View synonyms
      1. 1.1Break (an agreement or promise)
        ‘he accused the government of ratting on an earlier pledge’
        • ‘If we believe Gordon's account, as relayed through Robert Peston, Blair ratted on a promise to go by November of last year.’
        • ‘The press have also ratted on virtually every ‘deal’ they've ever entered into concerning a bit of privacy for William and Harry.’
        • ‘Whatever the cause, France ratted on his agreement, retaking Brest by force.’
        • ‘It is about the government ratting on an undertaking.’
        • ‘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.’
        • ‘President George Bush has ratted on the US commitment to reduce the pollution that is causing climate chaos across the globe.’
        • ‘Mind you, I had to do a bit of fast footwork to get the Foreign Office to rat on that fisheries deal that Jack Straw had done with Alex Salmond.’
        • ‘Allies of the Chancellor accused Downing Street of ratting on a deal struck between the two men to maintain a united front when dealing with Britain's pensions time bomb.’
        break, renege on, go back on, back out of, default on, welsh on
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Old English ræt, probably of Romance origin; reinforced in Middle English by Old French rat. The verb dates from the early 19th century.