The crypt of a church; an underground vault or chamber.

An underground vault, a crypt. (Also commonly in plural.)

An arched space under the floor of a church, used for ecclesiastical purposes; a crypt.

plural (rarely singular) A crypt, vault; esp. applied to the Chapel of St. Faith in St. Paul's Cathedral. (Cf. crowd, n.2) Now Historical.

A cavern, a crypt; (also) a covered or subterranean passage.

An underground cell, chamber, or vault; esp. one used as a burial place and typically lying beneath a church. Also: such a space used as a chapel…

A crypt under a church. Obsolete.