The mouth of the hearth of a blast furnace, through which the molten metal descends; formed by an arch of masonry (tymp-arch), or a block of…

an arch of masonry at the mouth of a blast furnace; cf. tymp arch at tymp, n. 1b.

A small opening in a furnace, through which the metal, or slag, or both, may be run out; also, a hole in a cementation furnace in which tap-bars (see…

a door or shutter that covers an opening giving access to a furnace.

(a) a tap-hole in a furnace; (b) a hole drilled in metal to be tapped or furnished with an internal screw-thread.

an indentation or opening in the side of a furnace, hearth, etc., to allow molten slag to run off.