It becomes more prominent and noticeable when the penis is erect.
First used on the popular comedy podcast Puke & the Gang.
Sometimes the second person will add their own feces to the original feces, resulting in a larger poop, which is rumored to add more fun.
The poop can sometimes be lodged in one persons anus, causing the sex act to end until the poop is dislodged, or an enima can remove it.
Usually practiced between gay males.