mule

Etymology 1

From Middle English mule, from Anglo-Norman mule and Old English mūl, both from Latin mūlus, from Proto-Indo-European *mukslós. Compare Late Latin muscellus (“young he-mule”), Old East Slavic мъшкъ (mŭškŭ, “mule”), Ancient Greek (Phocian) μυχλός (mukhlós, “he-ass”), and German Maul Maultier, Maulesel (through Latin).

noun

1. The generally sterile male or female hybrid offspring of a male donkey and a female horse.
   One day he ran into a herd of a half dozen elk, so he rode his mule down the canyon three or four miles, leaving the sheep alone. 2017, Robert S. McPherson, Cowboying In Canyon Country, Dog Ear Publishing, page 200
2. The generally sterile hybrid offspring of any two species of animals.
   It would be exceedingly interesting to know if the hybrid would reproduce, a matter I deem exceedingly doubtful, for the chances are it would prove a "mule" (infertile). 1922, Onnie Warren Smith, The Book of the Pike, page 187
3. (now rare) A hybrid plant.
   Vegetable mules supply an irrefragable argument in favour of the sexual system of botany. 1789, Erasmus Darwin, The Loves of the Plants, J. Johnson, page 149
   The most extraordinary mule, however, that is asserted to have been produced on the Continent, is a cross between the cabbage and horse-radish, which Monsieur Sageret reports that he has obtained […] 1837, William Herbert, Amaryllidaceæ: Preceded by an Attempt to Arrange the Monocotyledonous Orders, and Followed by a Treatise on Cross-bred Vegetables, and Supplement, page 353
4. (informal) A stubborn person.
   Where in the hell do you think I learned to be such a mule? 2005, Dorothea Benton Frank, Isle of Palms, Penguin
5. (slang) A person paid to smuggle drugs.
   Cocaine packet ingestion (these patients referred to as “mules”) may warrant surgery, Golytely or expectant passage. 2006, “Gastroenterology: Esophageal Foreign Bodies”, in Steven E. Diaz, The Little Black Book of Emergency Medicine (Jones and Bartlett's Little Black Book Series), 2nd edition, Sudbury, MA: Jones and Bartlett Publishers, page 101
   “Yeah, in Denver, we know about Uriarte's involvement in meth. Our Las Cruces office seized over six hundred pounds of methamphetamine from two of his mules last year.” 2007, Thomas G. Blacklock, Safe Zone: A Novel Approach to the Drug War, Xlibris Corporation, page 44
6. (numismatics) A coin or medal minted with obverse and reverse designs not normally seen on the same piece, either intentionally or in error.
   What is less clear, however, is why mint workers should have chosen to produce mules, if they were making forgeries […] 1988, Andrew Burnett, The Normanby hoard and other Roman coin hoards, British Museum Publications
7. (roleplaying games) A MMORPG character, or NPC companion in a tabletop RPG, used mainly to store extra inventory for the owner's primary character.
   He was in the middle of organizing his massive stash of rare and exquisite bounty, all kept safely in the inventory cache of a mule, an entirely separate character which he paid a monthly fee to maintain exclusively for that purpose. 2007, David L. McClard, Verotopia Online: The MMORPG of the Century, Xlibris, page 89
8. Any of a group of cocktails involving ginger ale or ginger beer, citrus juice, and various liquors.
9. (sailing) A kind of triangular sail for a yacht.
   In heavier seas where a boat must sail a course dictated by waves, or where wave action makes power more important than pointing, the mule will prove the faster sail. 1974, Yachting, volume 135, page 60
10. A kind of cotton-spinning machine.

verb

1. (transitive, slang) To smuggle (illegal drugs).
   There are many drug lords, each with his own corridor (think of it as a franchise of sorts) funneling narcotics into Texas. There are multifold methods of transport. The old, and still viable, way is to "mule" it across the Rio Grande in a small boat. 2000, Arturo Longoria, Keepers of the Wilderness
   Thornton was supposed to mule it back to the States from one of the ports he stopped in, give it to Maxwell and Ames, and get the second half of a quarter-million. 2004, William Glenn, The Sailor's Death

Etymology 2

From Middle French mule (“backless slipper”), from Medieval Latin mula (“slipper, shoe with a thick sole”), presumably from classical Latin mulleus, the dyed shoe of either the patricians or senators, from mūllus (“red mullet”) + -eus (“-y: forming adjectives”), from Ancient Greek μύλλος (múllos).

noun

1. Any shoe with an upper covering the front of the foot but without a back flap or strap, leaving the heel exposed.
   The bride was a shocking housekeeper and dragged round all day in boudoir cap, frowsy negligee and mules—slip, slop, slip, slop. 1944, Emily Carr, “First Tenant”, in The House of All Sorts
   Routine dress for Tuesday will be bra and panties with high-heel satin mules. 1946, George Johnston, Skyscrapers in the Mist, page 29