资料来源 : Webster's Revised Unabridged Dictionary (1913)

Scum \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.

资料来源 : WordNet®

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}]

scummed
     See {scum}