When in a football game, if one person misses a tackle and slaps the head of another man's penis by mistake.
"Dude! He just gave out a Fontana Head Slap!"
"Wow! He's not going to be able to have children after that Fontana Headslap!"
"Wow! He's not going to be able to have children after that Fontana Headslap!"
by Gil2011 August 21, 2011
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