informer
noun [ C ] uk/ɪnˈfɔː.mər/ us/ɪnˈfɔːr.mɚ/
告密者，举报人；（尤指警方的）线人
a person who gives information in secret, especially to the police
Most police informers receive a reward for their information. 大多数警方的线人都会因提供消息而获得报酬。
Synonyms: grass (PERSON) rat (PERSON) stool pigeon supergrass
Compare: blabbermouth fink noun tattletale telltale noun informant