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

While people mainly associate Rathlin Island with puffins, they have returned to the Isle of Muck nature reserve in County Antrim in recent years, after a rat eradication programme.

From BBC ● Aug. 15, 2026

This is a franchise that once saw its mascot give fans the finger and had two teammates blame a heated argument on a disagreement over the difference between a rat and a raccoon.

From The Wall Street Journal ● Jul. 22, 2026

They used the rat tapeworm Hymenolepis diminuta, a non-pathogenic species commonly used to study interactions among parasites, gut microorganisms, and the immune system because of its known anti-inflammatory properties.

From Science Daily ● Jul. 10, 2026

The long-tailed rat known as Oligoryzomys longicaudatus carries the Andes strain in Patagonia.

From Barron's ● May 15, 2026

“Hello and hello,” Clare said to each rat, rushing through pleasantries.

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

Like rats in a Skinner box being conditioned to get food or stop pain, AI models hill-climb in a process similar to reinforcement learning, tweaking their parameters based on feedback.

From The Wall Street Journal ● Aug. 14, 2026

Now, a burnt-out putrid warehouse that has devastated businesses and forced residents to remain inside their homes during a sweltering summer, as flies and giant rats infest the neighborhood.

From Los Angeles Times ● Aug. 8, 2026

Several people, including former rebel fighter Motaz al-Zaydi, told us they had resorted to eating rats.

From BBC ● Aug. 7, 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

The rats had dissipated and Clare had thought himself safe.

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

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

Simone now knew she had ratted him out.

From Seattle Times ● Oct. 16, 2022

They saw my fire on the live camera feed and ratted me out to the police.

From "Linked" by Gordon Korman

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

"I don't know how I feel about the culture of ratting out your neighbours," Ms Morfopoulos said.

From BBC ● Sep. 6, 2023

"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

But he has to know that if anyone hears a word about this, it’s just as bad as ratting on Aunt Pooh.

From "On the Come Up" by Angie Thomas