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ass 1 (ăs)
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n. pl. ass·es (ăsĭz)
1. Any of several hoofed mammals of the genus Equus, resembling and closely related to the horses but having a smaller build and longer ears, and including the domesticated donkey.
2. A foolish or stupid person.

[Middle English asse, from Old English assa, perhaps a hypocoristic for Old English dialectal (Northumbrian) asal, ultimately (perhaps via a Celtic form akin to Old Irish asal) from Latin asinus; see ASININE.]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2016 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 
ass 2 (ăs)
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n. pl. ass·es (ăsĭz)
Vulgar Slang
1.
a. The buttocks.
b. The anus.
2. Sexual intercourse.
adj. or assed (ăst)
Used in combination with adjectives as an intensive: I don't want to play your dumb-ass game. That is one crazy-ass idea.
Idiom:
have (one's) head up (one's) ass
To behave in an ignorant or foolish manner.

[Middle English ars, from Old English ears; see ors- in the Appendix of Indo-European roots.]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2016 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 

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