A space under the floor of an ancient Roman building where heat from a furnace
was accumulated to heat a room or a bath.
I learned this word from my critique partner, who does some excellent research and writes in historical-feeling fantasy worlds. Thanks, Amy Raby, for a great new vocab word!
Definition from http://education.yahoo.com/reference/dictionary/entry/hypocaust
Image from: http://en.wikipedia.org/wiki/Hypocaust