[scum] n [ME, fr. MD schum; akin to OHG scum foam] (14c) 1 a: extraneous matter or impurities risen to or formed on the surface of a liquid often as a foul filmy covering b: the scoria of metals in a molten state: dross c: a slimy film on a solid or gelatinous object
2. a: refuse b: a low, vile, or worthless person or group of people -- scum.my adj
[2]scum vi scummed ; scum.ming (1661): to become covered with or as if with scum