This is an extremely painful type of doody that is often accompanied by bleeding and/or blood streaks on the resulting poo stick.
A more common description of this type of doody states that it feels as though there are shards of glass juxtapositioned throughout the poo that sporadically slice your butthole lining as it exits. However, to be technically correct, shards of glass are inanimate and passive in nature, whereas the feeling described here is very much an animate and active process--it really does feel as though a moving blade is cutting you.
Note: painful symptoms of M.W.P. may present themselves during a P.O.U.S.