cav·ern 
(kăvərn)
(kăvərn)n.
1. A large cave.
2. A large underground chamber, as in a cave.
tr.v. cav·erned, cav·ern·ing, cav·erns
1. To enclose in or as if in a cavern.
2. To hollow out.
[Middle English caverne, from Old French, from Latin caverna, from cavus, hollow; see keuə- in the Appendix of Indo-European roots.]