Pulling your scrotum (nut sack) wide apart to expose the veins through light. To make it appear as a bat's wing.
My girlfriend came out of the shower to be exposed to a Bat Flap waiting in eagerness to be licked!
by HerNextBaby'sFather February 22, 2013
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Noun

The unwashed hanging underarm skin of a morbidly obese person. Such an ailment has a tendency to form yeast deposits. If gone untreated, extra yeast deposits will occur.
"Spreading his arms wide, The Fatman's herped bat flaps spread his yeast spores to the populace.
by The Bakinnator January 20, 2014
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A flap bat is a woman with large vulva flaps that doesn't know how to shut them
Charlotte is a flap bat, she's apparently been with half of the town
by Markbabi March 21, 2017
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