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it's a tan on your upper lip.
it's when the pigment on your upper lip darkens more than other places on your face- usually when you're in the sun.
its not darker hair, strictly darker skin. thus, a sunstashe
"you forgot to wax your upper lip. look like you gotta mustache"
"it's not a mustache. it's a sunstashe."
by rowstar9 December 08, 2009
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