\Scum\, n. [Of Scand. origin; cf. Dan. & Sw. skum, Icel.
sk?m, LG. schum, D. schuim, OHG. sc?m, G. schaum; probably
from a root meaning, to cover. [root]158. Cf. {Hide} skin,
{Meerschaum}, {Skim}, v., {Sky}.]
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 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. 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\, 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.