Source : Webster's Revised Unabridged Dictionary (1913)

Dam \Dam\, n. [Akin to OLG., D., & Dan. dam, G. & Sw. damm,
   Icel. dammr, and AS. fordemman to stop up, Goth.
   Fa['u]rdammjan.]
   1. A barrier to prevent the flow of a liquid; esp., a bank of
      earth, or wall of any kind, as of masonry or wood, built
      across a water course, to confine and keep back flowing
      water.

   2. (Metal.) A firebrick wall, or a stone, which forms the
      front of the hearth of a blast furnace.

   {Dam plate} (Blast Furnace), an iron plate in front of the
      dam, to strengthen it.

Dam \Dam\, n. [OE. dame mistress, lady; also, mother, dam. See
   {Dame}.]
   1. A female parent; -- used of beasts, especially of
      quadrupeds; sometimes applied in contempt to a human
      mother.

            Our sire and dam, now confined to horses, are a
            relic of this age (13th century) . . . .Dame is used
            of a hen; we now make a great difference between
            dame and dam.                         --T. L. K.
                                                  Oliphant.

            The dam runs lowing up end down, Looking the way her
            harmless young one went.              --Shak.

   2. A kind or crowned piece in the game of draughts.

Dam \Dam\, v. t. [imp. & p. p. {Dammed}; p. pr. & vb. n.
   {Damming}.]
   1. To obstruct or restrain the flow of, by a dam; to confine
      by constructing a dam, as a stream of water; -- generally
      used with in or up.

            I'll have the current in this place dammed up.
                                                  --Shak.

            A weight of earth that dams in the water.
                                                  --Mortimer.

   2. To shut up; to stop up; to close; to restrain.

            The strait pass was dammed With dead men hurt
            behind, and cowards.                  --Shak.

   {To dam out}, to keep out by means of a dam.

Source : WordNet®

dam
     n 1: a barrier constructed to contain the flow of water or to
          keep out the sea [syn: {dike}, {dyke}, {levee}]
     2: a metric unit of length equal to ten meters [syn: {decameter},
         {dekameter}, {decametre}, {dekametre}, {dkm}]
     3: female parent of an animal especially domestic livestock
     [also: {damming}, {dammed}]

dam
     v : obstruct with, or as if with, a dam; "dam the gorges of the
         Yangtse River" [syn: {dam up}]
     [also: {damming}, {dammed}]