rat

noun
\ ˈrat How to pronounce rat (audio) \

Definition of rat

 (Entry 1 of 2)

1a : any of numerous rodents (Rattus and related genera) differing from the related mice especially by considerably larger size
b : any of various similar rodents
2 : a contemptible person: such as
a : one who betrays or deserts friends or associates
3 : a pad over which a woman's hair is arranged
4 : a person who spends much time in a specified place a mall rat

rat

verb
ratted; ratting

Definition of rat (Entry 2 of 2)

intransitive verb

1 : to betray, desert, or inform on one's associates usually used with on
2 : to catch or hunt rats
3 : to work as a scab

transitive verb

1 : to give (hair) the effect of greater quantity (as by use of a rat)
2 : to inform on : turn in usually used with out ratted out his accomplice

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Other Words from rat

Noun

ratlike \ ˈrat-​ˌlīk How to pronounce ratlike (audio) \ adjective

Examples of rat in a Sentence

Noun

a dirty old building infested by rats and mice I can't believe that rat turned us in to the police! No one understands why she's with a rat like him. Every night he goes to work out with the other gym rats.

Verb

The teacher knows what we did, which means that somebody ratted.
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Recent Examples on the Web: Noun

So, your first step is admitting that you—like a rat with an unreliable cocaine lever 🤷🏻—are addicted to dumb social-media feedback. Mari Uyehara, Bon Appetit, "It’s Dinner, Put Down Your Goddamn Phone (Yes, You)," 5 Mar. 2018 This is the president of the US calling a witness who is cooperating w/his own DOJ a rat. Aaron Rupar, Vox, "James Comey unloads on House Republicans and Fox News," 17 Dec. 2018 Use a tiny, rat-tail comb to get the cleanest-looking split. Maya Allen, Marie Claire, "13 Gorgeous Cornrows Photos to Inspire Your Next Look," 30 Jan. 2019 Or maybe this whole situation is yet another piece of evidence that installing workers in an open-plan office builds camaraderie about as well as herding rats into an open-plan cage. Karla L. Miller, The Seattle Times, "How to deal with the office tattletale," 12 Dec. 2018 There are signs that San Franciscans, once eager to download the latest app and try the latest gadget, are wearying of their role as Silicon Valley’s lab rats. Trisha Thadani, San Francisco Chronicle, "London Breed as mayor has the tech industry excited. Will it last?," 15 June 2018 But the longstanding practice of exposing rabbits, rats, and other animals to chemicals to evaluate risks is facing growing public objections and cost concerns, helping spur a hunt for alternatives. Vanessa Zainzinger, Science | AAAS, "New digital chemical screening tool could help eliminate animal testing," 11 July 2018 The score, by Baltimore composer Dan Deacon, incorporates sounds generated by rats. Ed Stockly, latimes.com, "Monday's TV highlights: 'The Voice' on NBC," 26 Feb. 2018 Their simulations were based on how the disease would move depending on if it was transmitted by rats and fleas versus human parasites. Mika Mckinnon, Smithsonian, "Are Rats Innocent of Spreading the Black Plague?," 17 Jan. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'rat.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of rat

Noun

before the 12th century, in the meaning defined at sense 1a

Verb

1812, in the meaning defined at intransitive sense 1

History and Etymology for rat

Noun

Middle English rat, ratte, going back to Old English ræt (attested once), akin to Old Saxon ratta "rat," Middle Dutch ratte, rotte, Old High German ratta, radda, ratza (feminine weak nouns), also Old High German rato (masculine weak noun), probably going back to an ablauting paradigm *raþō (nominative), *rattaz/*ruttaz (genitive), *radeni/*rudeni (dative), going back to earlier *(H)rót-ōn, *(H)rt-n-ós, *(H)rt-én-i, of uncertain origin

Note: The origin of the etymon beyond Germanic is obscure. Regionally in German Ratz or Ratze are applied to other animals (as the dormouse and the polecat); if these senses are old, the application of the etymon to rats (Rattus rattus, Rattus norvegicus) may be secondary. Note that if the base is pre-Germanic *rat-, there is no connection to either Latin rōdere "gnaw, nibble, eat away" (see rodent) or rādere "scrape, shave" (see rase), as has often been assumed.

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More Definitions for rat

rat

noun

English Language Learners Definition of rat

 (Entry 1 of 2)

: a small animal that has a pointed nose and a long, thin tail
: a person who is not loyal or who cannot be trusted
: a person who is bad or cruel

rat

verb

English Language Learners Definition of rat (Entry 2 of 2)

informal : to tell someone in authority (such as the police) about something wrong that someone has done : to betray someone

rat

noun
\ ˈrat How to pronounce rat (audio) \

Kids Definition of rat

 (Entry 1 of 2)

1 : a gnawing animal with brown, black, white, or grayish fur that looks like but is larger than a mouse
2 : a person who betrays friends

rat

verb
ratted; ratting

Kids Definition of rat (Entry 2 of 2)

: to betray a friend

rat

noun
\ ˈrat How to pronounce rat (audio) \

Medical Definition of rat

: any of the numerous rodents (family Muridae) of Rattus and related genera that differ from the murid mice by their usually considerably larger size and by features of the teeth and other structures and that include forms (as the brown rat, the black rat, and the roof rat) which live in and about human habitations and in ships, have become naturalized by commerce in most parts of the world, and are destructive pests consuming or destroying vast quantities of food and other goods and acting as vectors of various diseases (as bubonic plague)

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More from Merriam-Webster on rat

Rhyming Dictionary: Words that rhyme with rat

Thesaurus: All synonyms and antonyms for rat

Spanish Central: Translation of rat

Nglish: Translation of rat for Spanish Speakers

Britannica English: Translation of rat for Arabic Speakers

Britannica.com: Encyclopedia article about rat

Comments on rat

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