1
a
: any of numerous rodents (Rattus and related genera) differing from the related mice especially by considerably larger size
b
: any of various similar rodents
2
: a contemptible person: such as
a
: one who betrays or deserts friends or associates
b
c
3
: a pad over which a woman's hair is arranged
4
: a person who spends much time in a specified place
a mall rat
ratted; ratting
1
: to betray, desert, or inform on one's associates
—usually used with on
2
: to catch or hunt rats
3
: to work as a scab
1
: to give (hair) the effect of greater quantity (as by use of a rat)
2
: to inform on : turn in
—usually used with out
ratted out his accomplice
Synonyms
Examples of rat in a Sentence
Noun
a dirty old building infested by rats and mice
I can't believe that rat turned us in to the police!
No one understands why she's with a rat like him.
Every night he goes to work out with the other gym rats.
Verb
The teacher knows what we did, which means that somebody ratted.
Recent Examples on the Web
Eduardo Cuevas, USA TODAY, 29 Oct. 2024
Multimammate rats often live in areas where food supplies are stored.
—Mary Kekatos, ABC News, 29 Oct. 2024
Some people also get sick after eating the rats themselves, according to the CDC.
—Jen Christensen, CNN, 28 Oct. 2024
The baby had over 50 rat bites covering his body, authorities said.
—Nicole Acosta, People.com, 26 Oct. 2024
See all Example Sentences for rat 
These examples are automatically compiled from online sources to
illustrate current usage. Opinions expressed in the examples do not represent those of
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Noun
Infections typically occur in the dry season, between December and April, following the reproduction cycle of the multimammate rat in the wet season, the World Health Organization said.
—Eduardo Cuevas, USA TODAY, 29 Oct. 2024
Multimammate rats often live in areas where food supplies are stored.
—Mary Kekatos, ABC News, 29 Oct. 2024
Some people also get sick after eating the rats themselves, according to the CDC.
—Jen Christensen, CNN, 28 Oct. 2024
The baby had over 50 rat bites covering his body, authorities said.
—Nicole Acosta, People.com, 26 Oct. 2024
See all Example Sentences for rat
Dictionary Entries Near rat
Cite this Entry
“Rat.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/rat. Accessed 7 Nov. 2024.
Copy CitationKids Definition
rat
1 of 2 noun1
: any of various rodents that have brown, black, white, or grayish fur and a long usually nearly hairless tail and that look like but are larger than the related mice
2
: a person who betrays friends
3
: a person who spends much time in a specified place
a mall rat
rat
2 of 2 verb
ratted; ratting
1
: to betray, desert, or inform on one's friends
didn't rat on us
ratted them out
2
: to catch or hunt rats
Medical Definition
rat
noun
: any of the numerous rodents (family Muridae) of Rattus and related genera that differ from the murid mice by their usually considerably larger size and by features of the teeth and other structures and that include forms (as the brown rat, the black rat, and the roof rat) which live in and about human habitations and in ships, have become naturalized by commerce in most parts of the world, and are destructive pests consuming or destroying vast quantities of food and other goods and acting as vectors of various diseases (as bubonic plague)
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