A mythological disease guaranteed to get you out of any event you don't want to go to. Often used by males to get out of their girlfriend's lameass plans.

Originated from Penny Arcade.
Girl: "So are you ready to go spend the day at the farmer's market?

Boy: "Sorry, I got a terrible case of Fisherman's Mouth. Seriously, you don't want this shit."
by ThePunkRockJester August 25, 2008
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