Hypocaust
Hypocaust , noun
[Latin hypocaustum, Greek {not transcribed}; {not transcribed} under + {not transcribed} to burn: compare French hypocauste.]
(Anc. Architecture) A furnace, esp. one connected with a series of small chambers and flues of tiles or other masonry through which the heat of a fire was distributed to rooms above. This contrivance, first used in bath, was afterwards adopted in private houses.