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1.
The name given to the vertical slit or opening at the front of guys' briefs or boxers, which allows quick access for masturbation ("fapping").
Frequent use of ones fap flap can overstretch the fabric leading to awkward and embarrassing sleeping positions.
by JakobTTx January 28, 2010
 
2.
Another word for the Magnetic Cover of the New iPad2.

The cover protects the screen during fapping.
"Dude, gruwesome."
"Fortunately only on my fap flap and not on the screen
by PIT5657 August 23, 2011