1. Animal resembling a small horse: a small domesticated member of the horse family with a gray or brown coat, long ears, and a large head. Latin name Equus asinus. The donkey was domesticated by the Egyptians about 4000 BC; it is more surefooted than the horse, which makes it better on mountain trails. The donkey can carry heavy loads and can go virtually anywhere. It lives longer than the horsegenerally from 25 to 50 years. The donkey can run up to 50 km/h (up to 30 mph).