The impurities of silver separated from the one in the process of melting (Prov. 25:4; 26:23; Ps. 119:119). It is also used to denote the base metal itself, probably before it is smelted, in Isa. 1:22, 25.
·noun Rust of metals. II. Dross ·noun Waste matter; any worthless matter separated from the better ...
Webster's Dictionary of the English Language