# rat

/ˈɹæt/ (US) · /ɹˈæt/ (UK)

Source: https://englishreference.com/word/rat
Updated: 2026-06-19

## Senses

### 1. the animal

noun · CEFR A2

a small animal with a long tail that looks like a large mouse.

For teachers: any of various medium-sized rodents, particularly those in the genus Rattus, characterized by a long hairless tail and a pointed snout.

- The old warehouse was full of rats looking for food in the rubbish.
- Urban planners must account for the resilience of rat populations when designing waste management systems for densely populated city centres.

### 2. a traitor or informant

noun · CEFR B2 · Informal

a person who is dishonest or betrays their friends or group.

For teachers: a person who betrays a person, group, or cause; often used for an informant who gives information to the police.

- He called his former partner a rat for telling the boss about the mistake.
- In many underworld narratives, the character identified as the rat often faces severe consequences for violating the code of silence.

### 5. to inform on someone

verb · CEFR B2 · Informal

to tell the police or someone in power about something bad another person did.

For teachers: to inform on someone or betray a secret to the authorities; often used with the preposition 'on'.

- He decided to rat on his friends to avoid going to jail.
- The witness was hesitant to rat on the gang members, fearing that the police could not provide adequate protection after the trial.

Usage: Usually takes the preposition 'on'.

### 6. to desert a cause

verb · CEFR C1 · Formal

to leave a group or a political party when they are in trouble.

For teachers: to desert or betray a political party, cause, or principle, especially for personal gain.

- Several members of the party chose to rat when the scandal became public.
- The prime minister accused the defectors of ratting on the administration during its most vulnerable hour.

## Examples

- A rat runs across the subway tracks.
- He was called a rat by his old friends after he testified against them in court.
- The novel's protagonist is a cornered rat, lashing out at a society that has offered him nothing but contempt and the constant threat of exposure.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.