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
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