mule

Concise Oxford English Dictionary © 2008 Oxford University Press:
mule1

▶noun

• 1 the offspring of a male donkey and a female horse, typically sterile. Compare with hinny1.

• 2 a hybrid plant or animal, especially a sterile one.

• 3 an obstinate person.

• 4 informal a courier for illegal drugs.

• 5 (also spinning mule) a kind of spinning machine producing yarn on spindles.

– origin OE mūl, prob. of Gmc origin, from L. mulus, mula.

Concise Oxford English Dictionary © 2008 Oxford University Press:
mule2

▶noun a slipper or light shoe without a back.

– origin C16: from Fr., ‘slipper’.