When both sides of your nutsack adheres to your inner-thigh.

Bat-wings are preventable by;
1. Washing your nutsack once in a while
2. Wearing tighty-whities or boxer briefs
3. Air cnditioning will stop the flow of heat and thus slow down the process of sweaty nuts.
When I wake up after a hot night/banging, I will typically wake up with bat-wings if I sleep in the buff or with loose boxers.

"Hey babe, wake up! Check this out! When I open my legs, it's like bat-wings!"
by R. Trelford March 18, 2005
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When the ball sack gets stuck to the side of the leg forming what seems to look like a bat wing.
I stood up and got a major bat wing.
by Brando January 29, 2003
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when a male's nutsack sticks to his leg due to sweat.
Usually happen's on a hot day or during a physical workout.
"Dude, I got some serious bat wing right now"
Very common at weddings while wearing a tuxedo.
Sometimes can be corrected without even touching the affected area with a simple leg shake. Other times might need to play a little pocket pool.
Severe cases call for immediate fondling of the genital area.
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by Jimmy Stix March 17, 2008
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The hanging flap under the arm seen on older women
The old lady had bat wings you could have tied a knot in.
by Edna Sweetlove July 30, 2010
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A woman with large and longer 'flapping' style vaginal skin
"That girl I was with with had some serious Bat Wings."
by JPDDDLLD September 17, 2008
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The result of stretching one's scrotum as wide as one can to create a winged effect.

Best when done in a hot shower... to obtain maximum stretchage.
Drop trou' and show me your Bat-wing!
by Nick Nathan August 4, 2006
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"She was hot, but when I went south of the border, I found the monster bat wings waitin' for me.
by Thor9 September 8, 2006
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