furnace UK /ˈfɜːnɪs/US /ˈfɝnɪs/noun 4verb 2forms 3 noun4 •An industrial heating device, such as for smelting metal or firing ceramics.Plans for the next phase include furnaces capable of inert atmospheres and partial vacuums. •(US, Canada) A device that provides heat for a building.HVAC services include furnace maintenance. •(informal, figurative) Any area that is excessively hot.The busy kitchen became a sweltering furnace. •(figurative) A place or time of punishment, affliction, or great trial; severe experience or discipline.For the Lorde toke you and broughte you out of the yernen fornace of Egipte, to be vnto him a people of enheritaunce, as it is come to passe this daye. — 1530 verb2 •To heat in a furnace. •To exhale like a furnace. formsfurnaced · furnacing · furnaces