rat

American  

[rat] / ræt /

noun

• rats
  plural

1. any of several long-tailed rodents of the family Muridae, of the genus Rattus and related genera, distinguished from the mouse by being larger.

2. any of various mammals similar to or related to the long-tailed rodents of the genus Rattus.

3. Slang. a scoundrel.

4. Slang.

   1. a person who abandons or betrays their party or associates, especially in a time of trouble.

   2. an informer.

   3. a scab laborer.

5. Slang. a person who frequents a specified place: gym rats.

   a mall rat;

   gym rats.

6. a pad with tapered ends formerly used in women's hairstyles to give the appearance of greater thickness.

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interjection

1. Slang. rats, (an exclamation of disappointment, disgust, or disbelief.)

verb (used without object)

• rats,
  present (3rd person singular)
• ratted,
  past participle,  past
• ratting
  present participle

1. Slang.

   1. to desert one's party or associates, especially in a time of trouble.

   2. to turn informer; squeal.

      He ratted on the gang, and the police arrested them.

   3. to work as a scab.

2. to hunt or catch rats.

verb (used with object)

• rats,
  present (3rd person singular)
• ratted,
  past participle,  past
• ratting
  present participle

1. to make (the hair) appear thicker by use of a small pad of material or by teasing.

verb phrase

1. rat out to inform on.

   He ratted out his partners in exchange for a lighter sentence.

idioms

1. smell a rat, to suspect or surmise treachery; have suspicion.

   After noting several discrepancies in his client's story, the attorney began to smell a rat.

rat British  

/ ræt /

noun

1. any of numerous long-tailed murine rodents, esp of the genus Rattus , that are similar to but larger than mice and are now distributed all over the world See also brown rat black rat

2. informal a person who deserts his or her friends or associates, esp in time of trouble

3. informal a worker who works during a strike; blackleg; scab

4. slang an informer; stool pigeon

5. informal a despicable person

6. to detect something suspicious

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verb

1. informal

   1. to divulge secret information (about); betray the trust (of)

   2. to default (on); abandon

      he ratted on the project at the last minute

2. to hunt and kill rats

rat More Idioms  

More idioms and phrases containing rat

• like a drowned rat
• smell a rat

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Other Word Forms

Derived Forms

• ratlike
  adjective

Inflected Forms

Nouns

• rats
  plural

Participles

• ratting
  present
• ratted
  past

Conjugated Forms

Present

• rat
  simple
• rats
  simple
• have ratted
  perfect
• has ratted
  perfect
• am ratting
  progressive
• are ratting
  progressive
• is ratting
  progressive
• have been ratting
  perfect progressive
• has been ratting
  perfect progressive

Past

• ratted
  simple
• had ratted
  perfect
• was ratting
  progressive
• were ratting
  progressive
• had been ratting
  perfect progressive

Future

• will rat
  simple
• will have ratted
  perfect
• will be ratting
  progressive
• will have been ratting
  perfect progressive

Etymology

Origin of rat

First recorded before 1000; Middle English rat(t)te, Old English ræt; cognate with Dutch rat, German Ratz, Ratte

Explanation

Rats are mouse-like rodents with long tails, pointed noses, and whiskers. Rats are often associated with filth and disease. So, if someone calls you a rat, it's not like being called a fox. It's an insult. Many people keep rats as pets, and scientists often study rats because their psychological behavior is actually very similar to that of humans. Rats are intelligent and adaptable, but wild rats also carry disease and sometimes bite humans. These negative traits have led to the informal meaning of rat, "hateful person," "liar," or "double-crosser." You can also use rat as a verb to mean "betray or snitch on."

Example Sentences

See Examples For:

rat rats ratted ratting

Khan also said there had been rats at the venue for a long time and that cleaners were told to check daily for rat droppings.

From BBC ● Sep. 29, 2026

Aiming to escape the rat race and find opportunities for work in a bleak job market, the founders use artificial intelligence to code, communicate with customers and promote their products.

From The Wall Street Journal ● Sep. 20, 2026

"Our younger generation... they're always in this little rat race, keeping up with social media," the 61-year-old said.

From Barron's ● Sep. 7, 2026

The researchers also currently obtain the EVs from primary rat astrocytes.

From Science Daily ● Sep. 4, 2026

The pile rustled and birthed another rat, smaller but with the same snowy fur and red eyes as her brother.

From "The Undead Fox of Deadwood Forest" by Aubrey Hartman

A venue of private members club Soho House is being investigated by the local council after a former member of staff raised concerns about rats and out-of-date food allegedly being served.

From BBC ● Sep. 29, 2026

A June 17 fire at cold storage operator Lineage’s 500,000-square-foot food warehouse left neighbors dealing with noxious smoke and an influx of rats and flies.

From Los Angeles Times ● Sep. 27, 2026

As the days went on, the smell worsened, drawing swarms of flies and rats to the neighborhood, where they pestered and sickened locals.

From Los Angeles Times ● Sep. 23, 2026

Warming oceans, habitat destruction, predation by rats and dogs, competition with commercial fisheries and accidental capture in fishing nets are also threatening many populations.

From Science Daily ● Sep. 22, 2026

The defenders followed the two rats closely, menacing them with staves.

From "Redwall" by Brian Jacques

No one would get ratted out on social media as “problematic.”

From The Wall Street Journal ● Feb. 21, 2026

The heavy black eyeliner and white-face makeup, the holey fishnets and ratted hair — these also serve as a beacon to fellow misfits, a way of finding your tribe while scaring off the normals.

From Los Angeles Times ● May 22, 2023

Finally, Perry himself turns on his schoolteacher girlfriend, Ginny Aimes, on a dime when the gun is brought to light, assuming she is the person who ratted him out.

From New York Times ● Apr. 10, 2023

Bulger, who ran the largely Irish mob in Boston in the 1970s and ’80s, served as an FBI informant who ratted on his gang’s main rival, according to the bureau.

From Seattle Times ● Aug. 23, 2022

But then I thought, so if it wasn’t Auggie who ratted me out, who was it?

From "Auggie & Me" by R. J. Palacio

And who wouldn’t have to modify their behavior if they thought Rover was ratting them out to his pals down at Paws & Claws?

From The Wall Street Journal ● Feb. 3, 2026

"But he could be ratting out Eastman and Powell, for example, in order to make a deal."

From Salon ● Jun. 29, 2023

This particular Planned Parenthood is where high school girls in my town would go if they needed birth control and didn’t want any busybodies ratting them out if they were spotted at the local clinic.

From Washington Post ● Jan. 27, 2023

With the Cambridge Analytica scandal still ratting along, Facebook revealed that a separate problem had exposed almost 50 million accounts to being hijacked.

From BBC ● Dec. 29, 2018

I finally got Mister Johnny out the way and now I have to worry about Miss Hilly coming over and ratting me out.

From "The Help" by Kathryn Stockett