Webster's Revised Unabridged Dictionary · 1913

Mule

Mule (mūl) , noun

[French, a she-mule, Latin mula, fem. of mulus; compare Greek my`klos, mychlo`s. Compare Anglo-Saxon mūl, from Latin mulus. Compare Mulatto.]

1.
(Zoology) A hybrid animal; specifically, one generated between an ass and a mare. Sometimes the term is applied to the offspring of a horse and a she-ass, but that hybrid is more properly termed a hinny. See Hinny.

Mules are much used as draught animals. They are hardy, and proverbial for stubbornness.

2.
(Botany) A plant or vegetable produced by impregnating the pistil of one species with the pollen or fecundating dust of another; -- called also hybrid.
3.
A very stubborn person.
4.
A machine, used in factories, for spinning cotton, wool, etc., into yarn or thread and winding it into cops; -- called also jenny and mule-jenny.
5.
A slipper that has no fitting around the heel.
Collocations (4)
Mule armadillo (Zoology) , a long-eared armadillo (Tatusia hybrida), native of Buenos Ayres; -- called also mulita. See Illust. under Armadillo.
Mule deer (Zoology) , a large deer (Cervus macrotis syn. Cariacus macrotis) of the Western United States. The name refers to its long ears.
Mule pulley (Machinery) , an idle pulley for guiding a belt which transmits motion between shafts that are not parallel.
Mule twist , cotton yarn in cops, as spun on a mule; -- in distinction from yarn spun on a throstle frame.