Slag

·vt The scoria of a volcano.

II. Slag ·vt The dross, or recrement, of a metal; also, vitrified cinders.

III. Slag ·add. ·vi & ·vt To form, or form into, a slag; to agglomerate when heated below the fusion point.

IV. Slag ·add. ·noun A product of smelting, containing, mostly as silicates, the substances not sought to be produced as matte or metal, and having a lower specific gravity than the latter;

— called also, ·esp. in iron smelting, cinder. The slag of iron blast furnaces is essentially silicate of calcium, magnesium, and aluminium; that of lead and copper smelting furnaces contains iron.