Donkey \Don"key\, n.; pl. Donkeys. [Prob. dun, in allusion to the color of the animal + a dim. termination.]

1. An ass; or (less frequently) a mule.

2. A stupid or obstinate fellow; an ass.

Donkey engine, a small auxiliary engine not used for propelling, but for pumping water into the boilers, raising heavy weights, and like purposes.

Donkey pump, a steam pump for feeding boilers, extinguishing fire, etc.; -- usually an auxiliary.

Donkey's eye (Bot.), the large round seed of the Mucuna pruriens, a tropical leguminous plant.

Source: Webster's Revised Unabridged Dictionary (1913)