Furnace (n.) : An inclosed place in which heat is produced by the
combustion of fuel, as for reducing ores or melting metals, for warming
a house, for baking pottery, etc.; as, an iron furnace; a hot-air
furnace; a glass furnace; a boiler furnace, etc.
Furnace (n.) : A place or time of punishment, affiction, or great trial; severe experience or discipline.
Furnace (n.) : To throw out, or exhale, as from a furnace; also, to put into a furnace.