grass up
In real, traceable use. Part of the curated seed collection; community review is coming.
Meaning · English
To betray by informing on.
Register: slang
Examples
My sister grassed me up to the caretaker! She thought she was doing me a favour — by grassing me up she was sure he'd let me off.
Usage example from English Wiktionary (CC BY-SA 4.0, retrieved 2026-07-30)
Sources & notes
Adapted from English Wiktionary (CC BY-SA 4.0, retrieved 2026-07-30 via kaikki.org).
Common questions
What does “grass up” mean?
To betray by informing on.
Is “grass up” formal or informal?
grass up is generally slang.