forehearth means the forward-facing extension or cavity of the hearth of a blast furnace, under the tymp. Lexicurio rates it Sui generis — a strength score of 87 out of 100.
Etymology
From fore- + hearth.
noun
- The forward-facing extension or cavity of the hearth of a blast furnace, under the tymp.“The lintel of the forehearth of the furnace bears the date 1753.”