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

b : scab sense 3b

c : informer sense 2

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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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.

Recent Examples on the Web: Noun The rat terrier/Chihuahua mix dogs, ranging in age from a few weeks to 2 years old, were found April 9 in an overstuffed crate measuring 48 inches long, 24 inches wide and 28 inches tall. — Tiffini Theisen, orlandosentinel.com, "Man arrested after 26 dogs stuffed in crate, left to die on dirt road in Florida," 26 Apr. 2021 In the lawsuit, Croft and her legal team said inmates complained about receiving food that was undercooked or not defrosted and contained rat, bird, or insect feces. — Justin Carissimo, CBS News, "Mississippi prisons end contract with controversial food provider," 26 Apr. 2021 That creates its own separate rat’s nest of issues beyond this article. — Joshua Stein, Forbes, "Unexpected Legal Risks Of Videoconferencing," 21 Apr. 2021 In the United States, rat poison is commonly used when trying to eliminate rats and mice, Ruder said. — Megan Marples, CNN, "Rat poison found in over 80% of bald eagles in a US study," 8 Apr. 2021 All people had to do was bring in a rat tail to be paid. — John Detrixhe, Quartz, "Jamie Dimon used the words “Latinx” and “carbon” for the first time in JPMorgan’s annual letter," 7 Apr. 2021 In 2019, the group called on government officials to declare a public health emergency after a survey of pest control companies showed increasing rat populations in the state. — Phil Diehl, San Diego Union-Tribune, "Talk-radio host announces Carlsbad recall effort," 5 Apr. 2021 Levee talks rat-a-tat fast, dispenses insults as sharp as the knife in his pocket. — Joe Morgenstern, WSJ, "‘Ma Rainey’s Black Bottom’ Review: Royal Blues," 17 Dec. 2020 Cecchine-Williams pointed to a rat hole near the base of a tree and a nearby bagel on the ground with small bites missing. — Conrad Swanson, The Denver Post, "Rats close park near Colorado Capitol after spike in homeless camping, Denver says," 15 Jan. 2020

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.

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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From the Editors at Merriam-Webster

Dictionary Entries near rat

Statistics for rat

Last Updated

13 May 2021

Cite this Entry

“Rat.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/rat. Accessed 18 May. 2021.

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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

See the full definition for rat in the English Language Learners Dictionary

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)