crypt

Short definition from Wiktionary

Noun

1. 1
   A cave or cavern.
2. 2
   An underground vault.
3. 3
   An underground vault: Especially: one beneath a church that is used as a burial chamber.
4. 4
   A small pit or cavity in the surface of an organ or other structure.
5. 5
   Any of the genus Cryptocoryne of aquatic plants of southern and southeastern Asia.
6. 6
   Any of the genus Cryptopus of orchids of Madagascar and Mauritius.