provocateur (n.)

"undercover agent who commits damning or illegal acts in the name of a group, or who encourages group members to commit them so as to damage its reputation or draw down punishment from authorities," 1915 (Emma Goldman), shortened form of agent provocateur "person hired to make trouble" (1845), from French provocateur, from Latin provocator "challenger," from provocare "to call out" (see provoke).

Related entries & more