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:
Gavin Newsom looks like the rat that Lisa Simpson accidentally shears thinking he’s a baby sheep.
From Slate ● Oct. 27, 2026
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
The researchers also currently obtain the EVs from primary rat astrocytes.
From Science Daily ● Sep. 4, 2026
According to Ivan’s description, a domovoi was a ghostly entity that would destroy the home unless appeased with sacrifices, and could shape-shift into a wolf or rat if it wanted.
From Anya and the Dragon by Sofiya Pasternack
Instead, they discovered that LDL concentrations in treated older rats also fell to levels observed in young animals.
From Science Daily ● Nov. 3, 2026
The discovery was made in rats, so further research is needed to determine whether the same changes occur in humans.
From Science Daily ● Oct. 26, 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
Cocoa barks at a couple of rats that run around.
From "The Manifestor Prophecy" by Angie Thomas
As a young woman in the 1920s, she disguised herself as a man and worked on a local archaeological dig at the Roman Villa Casale until she was ratted out and sent packing.
From The Wall Street Journal ● Aug. 21, 2026
"Bobb ratted out Corcoran," wrote national security attorney Bradley Moss.
From Salon ● Oct. 11, 2022
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
Among the $1 items found at the weekly Sunday sale at Jet Rag, I encountered the remains of ratted paraphernalia and uniforms distinct to the American ideology of waste.
From Los Angeles Times ● Dec. 1, 2021
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
"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
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
First, the regular student code about not ratting people out—that didn’t apply at the Academy.
From "Ungifted" by Gordon Korman
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Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
