In or pertaining to the lowest levels of a large house where the house staff work and are accommodated, contrasted with above stairs where the owning family reside.
Common, vulgar.
The areas of a large house in which house staff work, or the staff that work there.
An underground system of tunnels and chambers with recesses for graves, used (in former times) as a cemetery; a tunnel system used for burying the dead, as in Paris or Ancient Rome.