A conch is a shellfish with a large shell rather like a snail's. A conch or a conch shell is the shell of this creature.
conch in British English
(kɒŋk, kɒntʃ)
nounWord forms: pluralconchs (kɒŋks) or conches (ˈkɒntʃɪz)
1.
any of various tropical marine gastropod molluscs of the genus Strombus and related genera, esp S. gigas (giant conch), characterized by a large brightly coloured spiral shell
2.
the shell of such a mollusc, used as a trumpet
3. architecture another word for concha (sense 2)
Word origin
C16: from Latin concha, from Greek konkhē shellfish
conch in American English
(kɑŋk; kɑntʃ)
nounWord forms: pluralconchs (kɑŋks) or ˈconches (ˈkɑntʃɪz)
1.
a.
the large, spiral, univalve shell of any of various marine mollusks
b.
such a mollusk, often edible
2. Roman Mythology
such a shell used as a trumpet by the Tritons
3.
concha (sense 1)
4. US; [oftenC-]; Informal
a longtime resident of the Florida Keys, specif. of Key West
Word origin
ME conke < L concha < Gr konchē, mussel, shell < IE base *konkho- > Sans śankhá-, mussel