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¹rat

noun \ˈrat\

: 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

Full Definition of RAT

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

: a contemptible person: as

a : one who betrays or deserts friends or associates

b : scab 3b

c : informer 2

: a pad over which a woman's hair is arranged

: a person who spends much time in a specified place <a mall rat>

— rat·like \-ˌlīk\ adjective

See rat defined for English-language learners

See rat defined for kids

Origin of RAT

Middle English, from Old English ræt; akin to Old High German ratta rat and perhaps to Latin rodere to gnaw — more at rodent

First Known Use: before 12th century

Related to RAT

Synonyms: betrayer, canary [slang], deep throat, fink, informant, nark [British], informer, rat fink, snitch, snitcher, squealer, stoolie, stool pigeon, talebearer, tattler, tattletale, telltale, whistle-blower

Rhymes with RAT

bat, batt, blat, brat, cat, Cat, chat, chert, drat, fat, flat, frat, gat, gnat, hat, mat, Matt, matte, pat, phat, plait, plat, Pratt, sat, scat, scatt, skat, slat, spat, splat, sprat, stat, tat, that, vat

²rat

verb

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

rat·tedrat·ting

Full Definition of RAT

intransitive verb

: to betray, desert, or inform on one's associates —usually used with on

: to catch or hunt rats

: to work as a scab

transitive verb

: to give (hair) the effect of greater quantity (as by use of a rat)

: to inform on : turn in —usually used with out <ratted out his accomplice>

See rat defined for English-language learners

First Known Use of RAT

1812

RAT Defined for Kids

¹rat

noun \ˈrat\

Definition of RAT for Kids

: a gnawing animal with brown, black, white, or grayish fur that looks like but is larger than a mouse

: a person who betrays friends

²rat

verb

rat·tedrat·ting

Definition of RAT for Kids

: to betray a friend

Medical Dictionary

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)