Definition of "mule"
- noun
- A generally sterile male or female hybrid offspring of a male donkey and a female horse. 
- A generally sterile hybrid offspring of any two species of animals. 
- A stubborn person. 
- A person paid to smuggle drugs. 
- A coin or medal minted with obverse and reverse designs not normally seen on the same piece, either intentionally or in error. 
- A character on an MMORPG used mainly to store extra inventory of the owner's primary character. 
- A shoe that has no fitting or strap around the heel, but which covers the foot. 
- Sources