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

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Etymology

Origin of rat

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

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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

Gavin Newsom looks like the rat that Lisa Simpson accidentally shears thinking he’s a baby sheep.

From Slate ● Oct. 27, 2026

Anyone thought to be competing in the rat race is instinctively distrusted.

From The Wall Street Journal ● Oct. 26, 2026

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

From Science Daily ● Sep. 4, 2026

Tests have shown they can contain rat droppings and woodchips among other harmful substances.

From BBC ● Sep. 2, 2026

He was a regular pack rat, though smaller.

From "Secrets at Sea" by Richard Peck

Amyloid beta concentrations fell by approximately 50%, reaching levels comparable to those in young rats.

From Science Daily ● Nov. 3, 2026

In a new study involving older rats, researchers at the Keck School of Medicine of USC found that an experimental drug called cinaciguat reversed important signs of aging in specialized liver cells.

From Science Daily ● Nov. 3, 2026

Meanwhile on the Calf of Man, controlling rats - referred to locally as "longtails" to avoid bad luck - has helped the Manx shearwater recover to about 1,500 breeding pairs.

From BBC ● Oct. 25, 2026

U.S. attempts to tackle them, often using specialized soldiers called tunnel rats, largely failed.

From The Wall Street Journal ● Oct. 22, 2026

Scurvy rats, hungry ferrets, sly weasels, bad stoats—exactly what he needed.

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

Simone now knew she had ratted him out.

From Seattle Times ● Oct. 16, 2022

"Bobb ratted out Corcoran," wrote national security attorney Bradley Moss.

From Salon ● Oct. 11, 2022

Okay, apparently that girl had ratted him out.

From "The Darkest Minds" by Alexandra Bracken

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

Stroup has said that ratting out Peter Bourne was the “stupidest decision” he ever made.

From Slate ● Dec. 23, 2025

"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

The hard part was doing that without ratting on anyone.

From "Bodega Dreams" by Ernesto Quinonez

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