The definition of a mustache is hair on the upper lip.(noun)
When a man does not shave his upper lip, the hair growth on his lip is an example of a mustache.
See mustache in Webster's New World College Dictionary
Origin: Fr moustache < It mostacchio, mustache < MGr mustaki < Gr mystax, upper lip, mustache < mastax, a mouth, jaws < IE base *menth- > mouth
See mustache in American Heritage Dictionary 4
Origin: French moustache
Origin: , from Italian dialectal mustaccio
Origin: , from Medieval Greek moustakion
Origin: , from Greek mustax, mustache, upper lip.
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