1. any of various edible tropical marine gastropods of the genus Strombus having a brightly-colored spiral shell with large outer lip
The Collaborative International Dictionary of English v.0.48:
Conch \Conch\ (k[o^][ng]k), n. [L. concha, Gr. ko`gchh. See
1. (Zool.) A name applied to various marine univalve shells;
esp. to those of the genus Strombus, which are of large
size. Strombus gigas is the large pink West Indian
conch. The large king, queen, and cameo conchs are of the
genus Cassis. See Cameo and cameo conch.
Note: The conch is sometimes used as a horn or trumpet, as in
fogs at sea, or to call laborers from work.
2. In works of art, the shell used by Tritons as a trumpet.
3. [often capitalized] One of the white natives of the Bahama
Islands or one of their descendants in the Florida Keys;
-- so called from the commonness of the conch there, or
because they use it for food.
4. (Arch.) See Concha, n.
5. The external ear. See Concha, n., 2.