Boobstache

You know that sweat stain that ladies get under their boobs? The sweat pours down the central boob canal, and out the sides in the underboob regions - thus forming the sweatstain in the shape of a mustache... aka, the Boobstache.

"yo, check out the handlebar boobstache on the girl on the elliptical."

"eh, I'm looking at the porn boobstache on the girl twerking out on the treadmill!"