The residual shit stain that cannot be removed from one's underpants.
After several washes Dave's long poo stain remained apparent on his titey whiteys.
by Jeff February 12, 2004
2 more definitions
the action of wiping ones ass with a body part.
ohh look at lisa's wrist, what a poo stain!
by Me.me July 10, 2005
A person that has a small patch of discolorated hair on their head.
Check out the size of that kid's poostain!
by Rusty Shackleford May 25, 2003