an animal that has a female horse and a male donkey as parents, used especially for carrying loads 骡子 
Oxford Collocations Dictionaryadjective- pack
- stubborn
- team
- ride
- ride on
- bray
- carry something
- by mule
- on a/the mule
- (slang)
a person who is paid to take drugs illegally from one country to another 越境运毒者 a drug/drugs mule 毒品/毒品骡子 The authorities believe these men are important figures in the drug trade, not merely mules. 当局认为这些人是毒品交易中的重要人物，而不仅仅是骡子。
a slipper (= a soft shoe for wearing indoors) or a woman's shoe that is open around the heel （跟部敞开的）凉拖鞋
Word Originsenses 1 to 2 Old English mūl, probably of Germanic origin, from Latin mulus, mula; reinforced in Middle English by Old French mule.sense 3 mid 16th cent.: from French, ‘slipper’.