When you're smashing someone from behind and they then proceed to shit all over your dick with a putrid amount of diarrhea shit which fills the air around you as you inhale the glorious fumes of your girl, you feel at peace and one with nature.
I was smashing my girl from behind going in it raw and she gave me the poostank!
A weapon used to give someone a really nasty infection. Such as a Tooth Brush Fashioned into a prison shank then dipped into poop. The Toothbrush itself is fairly non lethal but the infection from the Poopshank will be deadly.
"Woman if you don't shut your mouthim gunna stab you with a Poopshank"