ha-ha /(ˈ)hɑˈhɑ/
  Ha-ha n.  A sunk fence; a fence, wall, or ditch, not visible till one is close upon it. [Written also haw-haw.]
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  ha-ha
       n 1: a loud laugh that sounds like a horse neighing [syn: hee-haw,
             horselaugh, haw-haw]
       2: a ditch with one side being a retaining wall; used to divide
          lands without defacing the landscape [syn: sunk fence, haw-haw]