slag

Waste material from a coal mine

Scum that forms on the surface of molten metal

Impurities formed and separated out when a metal is smelted from ore; vitrified cinders

Hard aggregate remaining as a residue from blast furnaces, sometimes used as a surfacing material

Scoria associated with a volcano

A coward

(chiefly Cockney) a contemptible person, a scumbag

A prostitute

A woman (sometimes a man) who has loose morals relating to sex; a slut

To produce slag

To become slag; to agglomerate when heated below the fusion point

To reduce to slag

(sometimes with "off") to talk badly about; to malign or denigrate (someone)

To spit