Clinker

Part of speech: noun

Pronunciation: /ˈklɪŋkə(ɹ)/

Definitions

1. A dense, tough substance formed from the combustion of various fuels
2. a byproduct of incomplete burning that is commonly found in heating systems or fireplaces
3. A hard mass left after burning fuel completely solidifies ; material that remains partly unburned in heating systems

Etymology: Clinker first meant a brick, not a lump of slag. Dutch sailors and brickmakers used "klinkaerd" for bricks fired so hard they rang when struck, and the name came from klinken, "to ring, resound." English borrowed the word in that sense, and it still names a hard, vitrified brick in some uses. The word then moved from the brickyard to the furnace. Hard, glassy lumps that collected in kilns and furnaces were given the same name, and in English it came to mean the dense, tough residue left when coal or other fuel burns. Anyone who has raked out a coal fire or a boiler has met the same material, which fused into a stony mass rather than burning away as ash. The English form "clinker" is also a suffix formation, from "clink" plus "-er," meaning something that clinks. The sense of a hard, ringing object runs through the whole history, from struck brick to cooled cinder.

Synonyms: brick, residue, ash, slag, scoria