donkeyn.[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.()