grass up
C1 slang separable transitive
In simple words
To tell the police or someone in charge that a person has done something wrong — seen as a big betrayal.
Meanings
1 C1
idiomatic
slang
To betray someone by informing on them to the police or another authority.
"He was grassed up by someone in his own crew."
Grammar: separable
Usage notes
British English slang. Interchangeable with 'grass on'. The separable form is notable: 'he grassed him up' rather than 'he grassed up him'. Very negative social connotation. Common in crime dramas and British vernacular.
Commonly used with
police mate dealer suspect gang teacher
Forms
Base
grass up
I/you/we/they
3rd person
grasses up
he/she/it
Past simple
grassed up
yesterday
Past participle
grassed up
have + pp
-ing form
grassing up
continuous
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