A series of pimples and or zits in the shape of a moustache. Probably caused by eating grasy food and not washing you face.
See also acnebeard
Eww look at that guy's acnestache!
My brother has a prominent acnestache.
His acnestache was a big turnoff.
When someone has a ton of acne above their upper lip, making it seem like they have a mustache made of acne. Is noticeable, but the acne usually isn't too bad.
Person 1: "Ew! That guy has such an acnestache.. he should grow a real one to cover it."
Person 2: "It's not that bad..."