Source : Webster's Revised Unabridged Dictionary (1913)

Pony \Po"ny\, n.; pl. {Ponies}. [Written also {poney}.] [Gael.
   ponaidh.]
   1. A small horse.

   2. Twenty-five pounds sterling. [Slang, Eng.]

   3. A translation or a key used to avoid study in getting
      lessons; a crib. [College Cant]

   4. A small glass of beer. [Slang]

   {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.

Source : WordNet®

pony
     n 1: a range horse of the western United States
     2: an informal term for a racehorse; "he liked to bet on the
        ponies"
     3: a literal translation used in studying a foreign language
        (often used illicitly) [syn: {trot}, {crib}]
     4: a small glass adequate to hold a single swallow of whiskey
        [syn: {shot glass}, {jigger}]
     5: any of various breeds of small gentle horses usually less
        than five feet high at the shoulder