Source : Webster's Revised Unabridged Dictionary (1913)

Cavern \Cav"ern\, n. [L. caverna, fr. cavus hollow: cf. F.
   caverne.]
   A large, deep, hollow place in the earth; a large cave.

Source : WordNet®

cavern
     n 1: any large dark enclosed space; "his eyes were dark caverns"
     2: a large cave or a large chamber in a cave

cavern
     v : hollow out as if making a cavern [syn: {cavern out}]