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1.
A guy who likes to shake his junk a lot. Especially while wearing loose fitting shorts so that their junk makes a slapping noise against their leg. This is often perfomed naked in front of mirrors.
Thelma: I caught Brad shaking his junk in front of the mirror when he got out of the shower.

Beth: OMG! He is such a cock flopper!
by mbaby13 December 18, 2009
 
2.
A fat or very ugly chick who causes stiff erections to flop.
Nicole is such a cock flopper no guy could ever keep it up around that slore.
by mbaby13 December 18, 2009
 
3.
female or instance that immediately makes your manhood floppy.
Fat people having sex, road kill, your mom knocking on your door when you're getting a BJ.

Those two slamhogs making out in public is a real Cockflopper.
by Jay Ownz September 27, 2010