The act of picking your ass for shit or sweat and going up to a buddy and sticking your finger in their ear and yelling POO WILLY! Very similar to the wet willy except for the source of material put on finger.
Ryan Garringer and John Nelson are homos so i gave their bitch asses a poo willy.
Sticking your index finger into your asshole and getting as much shit on it as possible, then going up to your friend and sticking the shit finger into their mouth.