Tentacle \Ten"ta*cle\, n. [NL. tentaculum, from L. tentare to handle, feel: cf. F. tentacule. See {Tempt}.] (Zo["o]l.) A more or less elongated process or organ, simple or branched, proceeding from the head or cephalic region of invertebrate animals, being either an organ of sense, prehension, or motion. {Tentacle sheath} (Zo["o]l.), a sheathlike structure around the base of the tentacles of many mollusks.