Clinker

1. n. A kind of brick. See Dutch clinker, under Dutch.
2. n. A mass composed of several bricks run together by the action of the fire in the kiln.
3. n. Scoria or vitrified incombustible matter, formed in a grate or furnace where anthracite coal in used; vitrified or burnt matter ejected from a volcano; slag.
4. n. A scale of oxide of iron, formed in forging.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.