sunk fence

from WordNet (r) 3.0 (2006)

sunk fence
    n 1: a ditch with one side being a retaining wall; used to
         divide lands without defacing the landscape [syn: {sunk
         fence}, {ha-ha}, {haw-haw}]

from The Collaborative International Dictionary of English v.0.48

Sunk \Sunk\,
   imp. & p. p. of {Sink}.
   [1913 Webster]

   {Sunk fence}, a ditch with a retaining wall, used to divide
      lands without defacing a landscape; a ha-ha.
      [1913 Webster]

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