rat

1 of 2

noun

ˈrat 

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 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

ratlike

ˈrat-ˌlīk 

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

Synonyms

Noun

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

Verb

• fink
• grass (on) [British slang]
• inform
• sing
• snitch
• split (on) [British]
• squeak
• squeal
• talk
• tell (on)

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

However, Flaco hit a building, then died from his injuries, as well as rat poison and pigeon herpes. —Andy Hoglund, EW.com, 31 Mar. 2024

The rats healed well after implantation, the scientists report, with the hair on the animals’ backs completely regrown after four weeks, with no obvious inflammation around the devices. —IEEE Spectrum, 27 Mar. 2024

Paul Calle, the Wildlife Conservation Society’s chief veterinarian, told The Washington Post that the virus, the rat poisons and the injuries Flaco suffered after flying into a building might have all contributed to the 13-year-old Eurasian eagle owl’s death. —Kyle Melnick, Washington Post, 27 Mar. 2024

That way, the rat has to work at getting the nut, which will trigger the trap. —Joan Morris, The Mercury News, 25 Mar. 2024

Studies on rats, rabbits and monkeys showed that these medications, if taken while pregnant, can lead to miscarriage and birth defects. —Katie Camero, USA TODAY, 21 Mar. 2024

The proprietor spent the rest of the day sifting through paperwork in his rat’s nest of a shop, under guard, ultimately producing next to nothing. —Paige Williams, The New Yorker, 18 Mar. 2024

Family Dollar, which is owned by Dollar Tree, was recently fined more than $40 million for a rat infestation at a warehouse that forced hundreds of stores to temporarily close. —Nathaniel Meyersohn, CNN, 13 Mar. 2024

Further study of rat heart cells suggests the new compounds do more strongly mimic the effects of exercise. —Lindsey Leake, Fortune Well, 18 Mar. 2024

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

Phrases Containing rat

• kangaroo rat
• lab/laboratory rat
• brown rat
• like a drowned rat
• naked mole rat
• pack rat
• rat-a-tat
• rat-bite fever
• mole rat
• rat run
• rat-tail file
• rug rat
• red rat snake
• rat trap cheese
• water rat
• rat-a-tat-tat
• rat race
• the rat race
• rat snake
• gray rat snake
• rat-arsed
• black rat snake
• western rat snake
• Norway rat
• rat cheese
• rat fink
• eastern rat snake
• wood rat
• smell a rat

Kids Definition

rat

1 of 2 noun

ˈrat 

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

-ˌlīk 

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

ˈrat 

: 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)