When a male has to shit so bad he gains an erection. This happens when one holds their pooh too long, all the pooh pushes up against the prostate; which leads to an erection.
Dude, i got a massive poop boner right now.

This poop boner is wicked!
by Synthroid December 09, 2010
Get a Poop Boner mug for your Facebook friend Julia.