The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   2. (Metal.) A firebrick wall, or a stone, which forms the
      front of the hearth of a blast furnace.
      [1913 Webster]

   Dam plate (Blast Furnace), an iron plate in front of the
      dam, to strengthen it.
      [1913 Webster]