Merriam-Webster Collegiate Dictionary - pony

 noun  (plural ponies)  Etymology: probably from obsolete French poulenet, diminutive of French poulain colt, from Old French pulain, perhaps from Medieval Latin pullamen young animal, from Latin pullus — more at foal  Date: 1659  1.  a. a small horse; especially one of any of several breeds of very small stocky animals noted for their gentleness and endurance  b. a bronco, mustang, or similar horse of the western United States  c. racehorse — usually used in plural  2. something smaller than standard: as  a. a small beer glass  b. a small liqueur glass typically holding one ounce  3. a literal translation of a foreign language text; especially one used surreptitiously by students in preparing or reciting lessons