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

More and more young people talk about feeling burnt out, question the point of staying in the rat race and, in some cases, feel bruised by their parents' tough love.

From BBC ● Jun. 13, 2026

Modern dating can feel like a rat race, where meetups are faster, cheaper and more abundant.

From The Wall Street Journal ● May 21, 2026

The Andes virus, which circulates in Argentina and Chile and is mainly spread among the long-tailed pygmy rice rat, is the only hantavirus strain known to be able to transmit from human to human.

From Los Angeles Times ● May 14, 2026

Guillermo Deferrari, of Ushuaia's scientific research center, downplayed the landfill theory, explaining that the colilargo is herbivore and lives off seeds and fruit found in forested ecosystems, not in dumps, where the common rat feeds.

From Barron's ● May 12, 2026

“I know where to take you,” said the rat, and he started scampering down the tunnel.

From "The Wild Robot Escapes" by Peter Brown

To determine whether orexin neurons directly influenced behavior, the scientists used optogenetics to control the neurons at the moment the rats expected a reward.

From Science Daily ● Aug. 5, 2026

Although the stimulation successfully activated the cells, it did not cause the rats to work harder or show any further rise in motivation.

From Science Daily ● Aug. 5, 2026

“We are still concerned about whether or not there is enough staffing to keep up with pest control,” the rats and flies, Rodarte said.

From Los Angeles Times ● Jul. 30, 2026

I spent most of my adult life near downtown Brooklyn, where my encounters with wildlife were limited to pigeons and rats.

From The Wall Street Journal ● Jul. 26, 2026

A wall was lined with giant sacks of sugar long since devoured by rats.

From "City Spies" by James Ponti

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

From The Wall Street Journal ● Feb. 21, 2026

“She ratted me out! Yes, I have the teapot, which I realize is quite the memento,” says Krasinski, writing while in production on an upcoming project.

From Los Angeles Times ● Mar. 24, 2025

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

Translation: none of Yates' neighbors ratted him out.

From Salon ● Apr. 4, 2020

Jilly, with her fat tummy showing between her shorts and her top, and Deidre, with her ratted hair and pink lipstick, moved closer.

From "It All Comes Down to This" by Karen English

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

Which is, you know, the problem here, and what all who tuned in should now be ratting him out for.

From Washington Post ● Oct. 21, 2019

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

First, the regular student code about not ratting people out—that didn’t apply at the Academy.

From "Ungifted" by Gordon Korman