ha-ha

from WordNet (r) 3.0 (2006)

ha-ha
    n 1: a loud laugh that sounds like a horse neighing [syn: {hee-
         haw}, {horselaugh}, {ha-ha}, {haw-haw}]
    2: 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

Ha-ha \Ha-ha"\ (h[aum]*h[aum]"), n. [See {Haw-haw}.]
   A sunk fence; a fence, wall, or ditch, not visible till one
   is close upon it. [Written also {haw-haw}.]
   [1913 Webster]

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