The Collaborative International Dictionary of English v.0.48:
Cavern \Cav"ern\, n. [L. caverna, fr. cavus hollow: cf. F. caverne.] A large, deep, hollow place in the earth; a large cave. [1913 Webster]WordNet (r) 3.0 (2006):
cavern n 1: any large dark enclosed space; "his eyes were dark caverns" 2: a large cave or a large chamber in a cave v 1: hollow out as if making a cavern [syn: cavern, cavern out]