1

rat

play
noun \ ˈrat \

Definition of rat

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
b :scab 3b
c :informer 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

ratlike

play \-ˌlīk\ adjective

Examples of rat in a Sentence

  1. a dirty old building infested by rats and mice

  2. I can't believe that rat turned us in to the police!

  3. No one understands why she's with a rat like him.

  4. Every night he goes to work out with the other gym rats.

Recent Examples of rat from the Web

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.

Origin and Etymology of rat

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.


2

rat

verb

Definition of rat

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

  1. The teacher knows what we did, which means that somebody ratted.

Recent Examples of rat from the Web

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.

First Known Use of rat

1812



RAT Defined for English Language Learners

rat

play
noun

Definition of rat for English Language Learners

  • : 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

Definition of rat for English Language Learners

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


RAT Defined for Kids

1

rat

play
noun \ ˈrat \

Definition of rat for Students

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

2

rat

verb

Definition of rat for Students

ratted; ratting
:to betray a friend

Medical Dictionary

rat

play
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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