mule1

noun

• 1the offspring of a donkey and a horse (strictly, a male donkey and a female horse), typically sterile and used as a beast of burden. Compare with hinny¹.
• a person compared to a mule, especially in being stubborn or obstinate.
• informal a courier for illegal drugs.
• a small tractor or locomotive, typically one that is electrically powered.

• 2a hybrid plant or animal, especially a sterile one.
• any of several standard crossbred varieties of sheep.

• 3 (also spinning mule) a kind of spinning machine producing yarn on spindles, invented by Samuel Crompton (1753–1827) in 1779.

• 4a coin with the obverse and reverse of designs not originally intended to be used together.