n. 1. The sterile hybrid offspring of a male donkey and a female horse, characterized by long ears and a short mane.
2. A sterile hybrid, as between a canary and other birds or between certain plants.
3. Informal A stubborn person.
4. A spinning machine that makes thread or yarn from fibers. Also called spinning mule.
5. A small, usually electric tractor or locomotive used for hauling over short distances.
6. Slang A person who serves as a courier of illegal drugs.