Slag /(slăg)/

1. The dross, or recrement, of a metal; also, vitrified cinders.
2. The scoria of a volcano.
3. 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. (Metal.)

imp. & p. p. Slagged; p. pr. & vb. n. Slagging

1. To form, or form into, a slag; to agglomerate when heated below the fusion point. (Metal.)