# grass up

CEFR C1 · Phrasal verb

Source: https://englishreference.com/word/grass-up
Updated: 2026-04-24

## Definition

to tell the police or someone in charge that another person has done something wrong. You use this when you think someone is being a 'snitch' or a 'rat'.

For teachers: to inform on someone to the authorities; marked British informal / slang, often carrying a negative connotation of betrayal within a peer group.

## Examples

- He refused to grass up his friends to the teacher.
- The thief was caught after his partner decided to grass him up to the police for a reward.
- In certain communities, the social pressure not to grass up one's neighbours remains significantly stronger than the fear of legal repercussions.

## Pitfalls

- Not "He grassed up to the police." but "He grassed them up to the police." — this phrasal verb usually requires an object to specify who is being informed on.

## Usage notes

- usually followed by an object (the person being reported) and often used with 'on'.
- Teaching tip: this is a highly regional British term; compare it with the American 'snitch on' or 'rat out' to show how different dialects handle the concept of informing.

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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.