Definition of pony
1a : 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 U.S.
c : RACEHORSE —usually used in plural
2 : something smaller than standard: such as
a : a small beer glass
b : a small liqueur glass typically holding one ounce