Meaning

• 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

Meaning

• 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