n. An informer providing substantial quantities of information on criminal or terrorist activities to the police.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a police informer who implicates many people
Word Usage
"Anderson has been named by a "supergrass" convicted of conspiracy to murder who will give evidence next week. marcpen: A supergrass is a high level ex-gang member who 'turns Queen's Evidence' to become a prosecution witness."