An informant is a person who provides privileged information about a person or organization to an agency. The term is usually used within the law enforcement world, where they are officially known as confidential or criminal informants (CI), and can often refer pejoratively to the supply of information without the consent of the other parties with the intent of malicious, personal or financial gain. However, the term is used in politics, industry and academia.
Read more about Informant: Criminal Informants, Labor and Social Movements, Politics, Jailhouse Informants, Terminology and Slang, List of Famous Informants