Real Dictionary

furnace
countable noun: A furnace is a container or enclosed space in which a very hot fire is made, for example to melt metal, burn rubbish, or produce steam.
singular noun: If you say that a place is a furnace, you mean that it is very hot there.

furnace in American English
an enclosed chamber or structure in which heat is produced, as by burning fuel, for warming a building, reducing ores and metals, etc.
noun: a structure or apparatus in which heat may be generated, as for heating houses, smelting ores, or producing steam
transitive verb: to heat (a metal piece) in a furnace

furnace in British English
noun: an enclosed chamber in which heat is produced to generate steam, destroy refuse, smelt or refine ores, etc

furnace in Chemical Engineering
noun: A furnace is a vessel in which there is a very high temperature.

furnace in Mechanical Engineering
noun: A furnace is an enclosed chamber in which heat is produced, for example to generate steam, burn waste, or produce molten metal.