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 more definition
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