The Collaborative International Dictionary of English v.0.48:

Pony \Po"ny\, n.; pl. Ponies. [Written also poney.] [Gael.
   ponaidh.]
   1. A small horse.
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   2. Twenty-five pounds sterling. [Slang, Eng.]
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   3. A translation or a key used to avoid study in getting
      lessons; a crib; a trot. [College Cant]
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   4. A small glass of beer. [Slang]
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   Pony chaise, a light, low chaise, drawn by a pony or a pair
      of ponies.

   Pony engine, a small locomotive for switching cars from one
      track to another. [U.S.]

   Pony truck (Locomotive Engine), a truck which has only two
      wheels.

   Pony truss (Bridge Building), a truss which has so little
      height that overhead bracing can not be used.
      [1913 Webster] poop
      poopoo