The Collaborative International Dictionary of English v.0.48:

Sow \Sow\, n. [OE. sowe, suwe, AS. sugu, akin to s[=u], D. zog,
   zeug, OHG. s[=u], G. sau, Icel. s[=y]r, Dan. so, Sw. sugga,
   so, L. sus. Gr. "y^s, sy^s, Zend. hu boar; probably from the
   root seen in Skr. s[=u] to beget, to bear; the animal being
   named in allusion to its fecundity. [root]294. Cf. Hyena,
   Soil to stain, Son, Swine.]
   1. (Zool.) The female of swine, or of the hog kind.
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   2. (Zool.) A sow bug.
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   3. (Metal.)
      (a) A channel or runner which receives the rows of molds
          in the pig bed.
      (b) The bar of metal which remains in such a runner.
      (c) A mass of solidified metal in a furnace hearth; a
          salamander.
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   4. (Mil.) A kind of covered shed, formerly used by besiegers
      in filling up and passing the ditch of a besieged place,
      sapping and mining the wall, or the like. --Craig.
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   Sow bread. (Bot.) See Cyclamen.

   Sow bug, or Sowbug (Zool.), any one of numerous species
      of terrestrial Isopoda belonging to Oniscus,
      Porcellio, and allied genera of the family Oniscidae.
      They feed chiefly on decaying vegetable substances.

   Sow thistle [AS. sugepistel] (Bot.), a composite plant
      (Sonchus oleraceus) said to be eaten by swine and some
      other animals.
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WordNet (r) 3.0 (2006):

sow bug
    n 1: terrestrial isopod having an oval segmented body (a shape
         like a sow)