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

Foam \Foam\, n. [OE. fam, fom, AS. f?m; akin to OHG. & G. feim.]
   The white substance, consisting of an aggregation of bubbles,
   which is formed on the surface of liquids, or in the mouth of
   an animal, by violent agitation or fermentation; froth;
   spume; scum; as, the foam of the sea.

   {Foam cock}, in steam boilers, a cock at the water level, to
      blow off impurities.