a subterranean chamber or vault, esp. one beneath the main floor of a church, used as a burial place, a location for secret meetings, etc.

Anatomy . a slender pit or recess; a small glandular cavity.

noun

catacomb , cave , cavern , cell , chamber , compartment , grave , grotto , mausoleum , room , sepulcher , tomb , undercroft , vault , cinerarium , ossuary , sepulture , cavity , follicle , pit , recess