Meaning & use
rat
Last updated
Meanings
nouncountable
A long-tailed rodent larger than a mouse, often seen as a pest.
Grammar: Plural rats: the rats hid in the cellar.
Patterns
- rats in something
A rat scurried along the wall of the alley.
The farmer set traps to catch the rats in the barn.
Laboratory rats are used in many medical studies.
nouncountableinformaldisapproving
A disloyal person who tells on friends or betrays them.
Grammar: Insulting; used about a person, as in 'he is a rat'.
Patterns
- a rat for something
Everyone called him a rat after he told the teacher.
She felt like a rat for breaking her promise.
The gang suspected there was a rat among them.
verbintransitiveinformal
To inform on someone, usually to a person in authority.
Grammar: Usually rat on someone: he ratted on his friends.
Patterns
- rat on someone
- rat someone out
Nobody wanted to rat on the others.
He ratted on his brother to their parents.
The witness ratted out the whole group.
Word forms
| plural | rats |
|---|---|
| third person singular | rats |
| past tense | ratted |
| -ing form | ratting |
Common combinations
- rat on someone
- Don't rat on your friends.
- rat race
- They left the rat race for a quiet farm.
- smell a rat
- I smelled a rat when the price seemed too good.
- lab rat
- The lab rat learned the maze quickly.
- rat poison
- Keep rat poison away from children.
Synonyms and how they differ
- rodent
- Rodent is the scientific group that includes rats, mice and squirrels, so it is broader than rat.
- informer
- Informer is a neutral, formal word for someone who tells on others, while rat is a rude insult.
- snitch
- Snitch is also informal but milder and often used among children.
- traitor
- Traitor suggests a serious betrayal of a country or cause, which is heavier than rat.
Opposites
Word family
Commonly confused: rat or mouse?
rat vs mouse
A mouse is a smaller rodent; a rat is larger with a longer, thicker tail.
Practice
Tom promised not to tell, but he ______ on us to the principal.
Choose one answer.
Rat on someone means to inform on them. Rated is a similar-sounding word meaning to judge, which does not fit with 'on us'.
Make it your own
Write a sentence using “rat”, then check it and compare it with the examples above.