a large marine gastropod mollusc with a spiral shell
any of numerous species of large marine gastropod molluscs: family Strombidae
the spiral shell of such a mollusc
in architecture, an apse, or the plain semidome of an apse
[Latin concha mussel, mussel shell, from Greek konchē; (sense 2) Italian conca semidome, apse, via late Latin from Latin concha]