Pooping when a fart is trapped behind the poop. The fart actually propels the poop out quicker. OR When you are unsure whether you need to poop or fart. Sometimes it's just one or the other. It is often a surprise.
I poop farted today and it was like blowing a bowling ball out of my butt.
I thought I needed to take a poop but it was just a poop fart.