Lu"nule (?), n. [F., fr. L. lunula, dim. of luna moon.] 1. (Anat.) Anything crescent-shaped; a crescent-shaped part or mark; a lunula; a lune.

2. (Chem.) A lune. See Lune.

3. (Zoöl.) (a) A small or narrow crescent. (b) A special area in front of the beak of many bivalve shells. It sometimes has the shape of a double crescent, but is oftener heart-shaped. See Illust. of Bivalve.