What does grassing mean?
Grassing is an informal word for following and watching someone, particularly when the watcher is police or is monitoring a person of investigative interest. In British and Irish usage, it can also describe informing on someone to the authorities, especially by disclosing information about a crime or an accomplice. The term is therefore associated with both surveillance and betrayal, two activities that may occasionally overlap. It is chiefly a piece of police, criminal, and underworld slang rather than formal vocabulary, and its connotations range from neutral in a report about surveillance to strongly disapproving when it describes someone who has informed on an associate. “Grassing” is worth knowing because it captures a specific kind of covert watching while also reflecting a long-standing vocabulary of police and criminal culture.
The informal practice of following or watching someone, especially a person being monitored by police; in some contexts, the act of informing on another person.
"The report alleged that the witnesses were being subjected to continuous police grassing."
Usually an uncountable noun. The surveillance sense is chiefly associated with British and Irish police usage.
To follow or monitor someone covertly, especially as police activity; also, informally, to inform on another person.
"Plainclothes officers spent the night grassing the suspect."
The word is informal. “Grassing on” is particularly associated with informing on an associate, while the surveillance use typically takes a person as its object.
“Grassing” is normally treated as an uncountable activity or practice, so it does not have a regular plural.
"There was widespread police grassing outside the courthouse."
In police slang, being grassed can mean that the long shadow of surveillance has already found you.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does grassing come from?
“Grassing” is a modern English formation on the slang word “grass,” an older informal term for a police informer; the “informing” sense of “grassing” developed directly from that vocabulary. The precise origin of the police-surveillance sense is less clearly documented, although it belongs to the same informal police and criminal register. The ordinary vegetation word “grass,” by contrast, descends from Old English gærs and is cognate with Dutch gras and German Gras.
How grassing is actually used
This is informal and context-dependent vocabulary, not a neutral term for routine observation. The surveillance sense is especially associated with British police usage, while the informing sense often carries a negative or derogatory implication because it suggests betraying an associate. The word may also be encountered in discussions of organized crime and police procedure.
Easily confused with grassing
Grassing means watching or informing on someone, whereas gassing means talking at length about something, especially in British English.