(1):

(n.) 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.

(2):

(n.) A small or narrow crescent.

(3):

(n.) A lune. See Lune.

(4):

(n.) Anything crescent-shaped; a crescent-shaped part or mark; a lunula, a lune.