Meaning of SLAG in English

By-product formed in smelting , welding , and other metallurgical and combustion processes from impurities in the metals or ores being treated.

Slag consists mostly of mixed oxidation-reduction ) by the atmosphere and keeping it clean. Slag cools into a coarse aggregate used in certain concretes; it is used as a road-building material, as ballast, and as a source of available phosphate fertilizer.

Britannica English dictionary.      Английский словарь Британика.