%hypocaust%

n. [ L. hypocaustum, Gr. &unr_;; &unr_; under + &unr_; to burn: cf. F. hypocauste. ] (Anc. Arch.) 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. [ 1913 Webster ]