Definition of: tentacle

(ten′tə·kəl) noun
1. Zool. A protruding flexible process or appendage (usually of the head) of invertebrate animals, functioning as an organ of touch, prehension, or motion. Some examples are the hollow fleshy processes about the mouth of a polyp communicating with the body cavity, the eyestalks of a gastropod, and the arms of a cuttlefish, especially one of the two longer arms of a decapod.
2. Bot. A sensitive glandular hair, as on the leaves of the sundew.
3. Something resembling a tentacle; a tendril. Also ten·tac·u·lum (ten·tak′yə·ləm). [<L tentaculum <tentare touch, try]
—ten·tac′u·lar adjective