supergrass
noun /ˈsuːpəɡrɑːs/
/ˈsuːpərɡræs/
(British English, informal)- a criminal who informs the police about the activities of a large number of other criminals, usually in order to get a less severe punishment
compare grassTopics Crime and punishmentc2(为求得宽大处理)向警方告密的罪犯