ter·ror·ist /ˈtɛrərɪst/ [ter-er-ist]
–noun 1. a person, usually a member of a group, who uses or advocates terrorism.
2. a person who terrorizes or frightens others.
3. (formerly) a member of a political group in Russia aiming at the demoralization of the government by terror.
4. an agent or partisan of the revolutionary tribunal during the Reign of Terror in France.
–adjective 5. of, pertaining to, or characteristic of terrorism or terrorists: terrorist tactics.

[Origin: 1785–95; terror + -ist; cf. F terroriste]

—Related forms
ter·ror·is·tic, adjective