Cockslapping is the practice is slapping someone's face with your penis, usually when erect. Often performed as a joke, when the recipient is either asleep, stoned, or otherwise incapacitated.
AS the title states it is the act in which the pennis is whacked furtively about the famouspainting the "mona lisa" often resulting in architectural fapping.
Architect 1: Look that dude's cockslapping the mona lisa!
Architect 2: Yeah, you like that don't you baby?! *fap fap fap*