Informant
An informant (also called an informer or, as a slang term, a "snitch", "rat", "stool pigeon" or "stoolie" ) is a person who tells someone private information about other people. This information is often damaging to the other people. It is meant to be information that is secret. The information is normally about a person, group or organization. It is given to an agency, often a government or law enforcement agency. The term is normally used in the law-enforcement world. In law enforcement, informants are known as confidential human sources (CHS), or criminal informants (CI).