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.