A short, rounded peice of fecal matter that disengages itself from the mass and falls separately from the mass. Most commonly seen in pets, especially dogs. It's often seen dropped on the floor after successfully defacating outside. More often than not, it's the final peice of feces of the total mass.
Uh oh!! There's a tudball on the carpet! Where's that dog?! I'm not pickin' that thing up.