Definition of: scum

(skum) noun
1. Impure or extraneous matter that rises to the surface of boiling or fermenting liquids.
2. Minute vegetation on stagnant water.
3. Scoria or dross of molten metals; also, foam; froth.
4. Figuratively, vile element; refuse. See synonyms under WASTE.
—v. scummed, scum·ming v.t. To take scum from; skim.
—v.i. To become covered with or form scum. [<MDu. schuum]
—scum′mer noun
—scum′my adjective