rat
Americannoun
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rats
plural
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any of several long-tailed rodents of the family Muridae, of the genus Rattus and related genera, distinguished from the mouse by being larger.
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any of various mammals similar to or related to the long-tailed rodents of the genus Rattus.
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Slang. a scoundrel.
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Slang.
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a person who abandons or betrays their party or associates, especially in a time of trouble.
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an informer.
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a scab laborer.
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Slang. a person who frequents a specified place: gym rats.
a mall rat;
gym rats.
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a pad with tapered ends formerly used in women's hairstyles to give the appearance of greater thickness.
interjection
verb (used without object)
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rats,
present (3rd person singular)
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ratted,
past participle, past
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ratting
present participle
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Slang.
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to desert one's party or associates, especially in a time of trouble.
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to turn informer; squeal.
He ratted on the gang, and the police arrested them.
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to work as a scab.
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to hunt or catch rats.
verb (used with object)
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rats,
present (3rd person singular)
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ratted,
past participle, past
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ratting
present participle
verb phrase
idioms
noun
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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
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informal a person who deserts his or her friends or associates, esp in time of trouble
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informal a worker who works during a strike; blackleg; scab
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slang an informer; stool pigeon
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informal a despicable person
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to detect something suspicious
verb
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informal
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to divulge secret information (about); betray the trust (of)
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to default (on); abandon
he ratted on the project at the last minute
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to hunt and kill rats
Other Word Forms
Derived Forms
Inflected Forms
Nouns
Participles
Conjugated Forms
Present
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ratsimple
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ratssimple
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have rattedperfect
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has rattedperfect
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am rattingprogressive
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are rattingprogressive
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is rattingprogressive
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have been rattingperfect progressive
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has been rattingperfect progressive
Past
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rattedsimple
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had rattedperfect
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was rattingprogressive
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were rattingprogressive
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had been rattingperfect progressive
Future
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
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
"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
“It’s hurtful, because the people who are calling me rat and snitch, they’re all officers,” he said.
From Los Angeles Times ● Aug. 26, 2026
Some moves were driven by other considerations, like an apartment with a rat infestation.
From MarketWatch ● Aug. 26, 2026
His deceit was uncovered when Helen's son smelt a rat and applied for Clare's Law, external, where you can ask if someone has a history of abusive offending.
From BBC ● Jul. 15, 2026
“This is what a rat brings his lunch in.”
From "Fourth Grade Rats" by Jerry Spinelli
Moore begins with a whisper and builds to a roar as Mona improvises a manic rant that involves rats and the plague.
From Los Angeles Times ● Sep. 7, 2026
He says those sourcing fake versions are in effect behaving as lab rats without any medical oversight.
From BBC ● Sep. 4, 2026
A June 17 fire at cold storage operator Lineage’s 500,000-square-foot food warehouse left the community with noxious smoke and an influx of rats and flies attracted to rotting meat.
From Los Angeles Times ● Sep. 1, 2026
They compared diabetic rats treated with curcumin with diabetic rats that did not receive the compound.
From Science Daily ● Aug. 26, 2026
It was, categorically, not the rats that he needed to fear.
From "Night Owls" by A.R. Vishny
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
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
“Tell me how I ratted, came home to a big bag,” he shrieks.
From New York Times ● May 20, 2020
When someone ratted on him, the police questioned Cole.
From "Touching Spirit Bear" by Ben Mikaelsen
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
He prided himself on not ratting out his Watergate co-conspirators and argued that if everyone had just shut up about it Nixon would not have been deposed.
From Washington Post ● Mar. 31, 2021
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
“Are the police here because of me ratting out Junito yesterday? Oh my God, is Beatriz here? What about the Latin Diablos?”
From "Like Vanessa" by Tami Charles
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
