What does "pony" mean?

Additional senses

1. 2.A translation or a key used to avoid study in getting lessons; a crib. [College Cant]
2. 3.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.