The Collaborative International Dictionary of English v.0.48:

Plow \Plow\, Plough \Plough\, v. t. [imp. & p. p. Plowed
   (ploud) or Ploughed; p. pr. & vb. n. Plowing or
   Ploughing.]
   1. To turn up, break up, or trench, with a plow; to till
      with, or as with, a plow; as, to plow the ground; to plow
      a field.
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   2. To furrow; to make furrows, grooves, or ridges in; to run
      through, as in sailing.
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            Let patient Octavia plow thy visage up
            With her prepared nails.              --Shak.
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            With speed we plow the watery way.    --Pope.
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   3. (Bookbinding) To trim, or shave off the edges of, as a
      book or paper, with a plow. See Plow, n., 5.
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   4. (Joinery) To cut a groove in, as in a plank, or the edge
      of a board; especially, a rectangular groove to receive
      the end of a shelf or tread, the edge of a panel, a
      tongue, etc.
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   To plow in, to cover by plowing; as, to plow in wheat.

   To plow up, to turn out of the ground by plowing.
      [1913 Webster] Plow

WordNet (r) 3.0 (2006):

ploughing
    n 1: tilling the land with a plow; "he hired someone to do the
         plowing for him" [syn: plowing, ploughing]