rat

noun
\ ˈrat \

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 \ 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

In general, avoid adding any meat, dairy, bones, or pet feces to your compost as these scraps can attract pests like rats or insects, says Thania Avelar, education coordinator at the South Coast Botanic Garden in California. Audrey Bruno, SELF, "How to Start Composting," 8 Jan. 2019 For some reason, every book in the self-improvement genre veers into evolutionary biology or what some study about dopamine and rats tells us about human accomplishment. Kate Bachelder Odell, WSJ, "‘Atomic Habits’ and ‘The Bullet Journal Method’ Review: New Year’s Baby Steps," 31 Dec. 2018 Many species of cockroaches and rats have also become nocturnal. Rob Dunn, Discover Magazine, "Our Attempts to Eradicate Insects are Just Making them Resistant to Pesticides," 16 Nov. 2018 In fact, that's what usually happens in human cases of rat lungworm. Eleanor Hildebrandt, Popular Mechanics, "How Parasites Can Lie Dormant for Years Before Killing You," 6 Nov. 2018 In fact, Bulletproof draws on studies done with rats to make their claims about metabolism and energy burn. Jaclyn London, Ms, Rd, Cdn, Good Housekeeping, "The Truth About Bulletproof Coffee, According to a Nutritionist," 5 Nov. 2018 The other islands are rat free and contain huge colonies of seabirds. Jason Daley, Smithsonian, "Coral Reefs Need Fewer Rats and More Bird Poo," 12 July 2018 We like Phillies manager Gabe Kapler’s idea of a prepared position player working an inning to save the bullpen in a blowout loss, but pitchers and their valuable arms should not be treated as lab rats. Bill Shaikin, latimes.com, "Three up, three down: Could there be a second round of Mannywood? Are the Indians invisible?," 7 July 2018 In female rats and male and female mice, the link between cancers and exposure to cellphone radiation was less clear, the researchers said. Sarah Krouse, WSJ, "Scientists Find ‘Clear Evidence’ Cellphone Radiation Can Cause Cancer in Rats," 1 Nov. 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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Learn More about rat

Dictionary Entries near rat

raster

rastik

rasure

rat

rat's ass

rat's-tail fescue

rata

Statistics for rat

Last Updated

15 Jan 2019

Look-up Popularity

Time Traveler for rat

The first known use of rat was before the 12th century

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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)

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

rat

noun
\ ˈrat \

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 \

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

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