Definitions by Remy Leus

Flappy Bird 

The act of stretching out your ball sack like a trampoline, and using it to bounce your flaccid (or partially flaccid (see half-chub)) penis up and down.

See: flappy bird nest

Mike Hawk: Dude I was bored the other day so I started playing with my flappy bird.
Jack Mehoff: Me too! But I bounced it too hard and sac taped myself.

Flappy Bird by Remy Leus January 30, 2014