rat

1 of 2

noun

1
a
: 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
ratlike adjective

rat

2 of 2

verb

ratted; ratting

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

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
It is transmitted by fleas often carried by rodents in the wild, including rats and prairie dogs. Eduardo Cuevas, USA TODAY, 9 July 2024 Makes more sense in France than a rat in the kitchen does. Dewayne Bevil, Orlando Sentinel, 8 July 2024 The rat threat alone! Hit the comments with your answers and any TV Qs of your own! Charlie Mason, TVLine, 5 July 2024 This led to talk of wharf rats, New York City rats, black widows, brown recluses, and the redback spiders of Australia, but, as inevitably happens with elvermen, the conversation returned to eels. Paige Williams, The New Yorker, 17 June 2024 See all Example Sentences for rat 

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'rat.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

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.

First Known Use

Noun

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

Verb

1812, in the meaning defined at intransitive sense 1

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

Dictionary Entries Near rat

Cite this Entry

“Rat.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/rat. Accessed 23 Jul. 2024.

Kids Definition

rat

1 of 2 noun
1
: any of various rodents that have brown, black, white, or grayish fur and a long usually nearly hairless tail and that look like but are larger than the related mice
2
: a person who betrays friends
3
: a person who spends much time in a specified place
a mall rat
ratlike adjective

rat

2 of 2 verb
ratted; ratting
1
: to betray, desert, or inform on one's friends
didn't rat on us
ratted them out
2
: to catch or hunt rats

Medical Definition

rat

noun
: 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)

More from Merriam-Webster on rat

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