scum /ˈskʌm/
 浮渣,糟粕,泡沫(vt.)將浮渣去除掉(vi.)產生泡沫
 Scum, v. t. [imp. & p. p. Scummed p. pr. & vb. n. Scumming ]
 1. To take the scum from; to clear off the impure matter from the surface of; to skim.
    You that scum the molten lead.   --Dryden & Lee.
 2. To sweep or range over the surface of. [Obs.]
    Wandering up and down without certain seat, they lived by scumming those seas and shores as pirates.   --Milton.
 Scum n.
 1. The extraneous matter or impurities which rise to the surface of liquids in boiling or fermentation, or which form on the surface by other means; also, the scoria of metals in a molten state; dross.
    Some to remove the scum as it did rise.   --Spenser.
 2. refuse; recrement; anything vile or worthless.
    The great and innocent are insulted by the scum and refuse of the people.   --Addison.
 Scum, v. i. To form a scum; to become covered with scum. Also used figuratively.
    Life, and the interest of life, have stagnated and scummed over.   --A. K. H. Boyd.
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 scum
      n 1: worthless people [syn: trash]
      2: a film of impurities or vegetation that can form on the
         surface of a liquid
      [also: scumming, scummed]