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2.
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 21, 2013
 
1.
When a man's scrotum attaches itself to the his thighs. Can be cured with ample amounts of baby powder
Damn it's hot. I have wicked batflaps.
by CSmizzle June 15, 2010