Poop is a term that is a synonym of "poo" or "feces". Poop is predominantly used informally and often by children in North America.
Poop is pronounced exactly as it is read.
A lesser known definition of poop is also that it is the highest and aftermost deck on a ship. However, to the layman this may cause occasional misunderstandings, such as when you say "the captain is standing on the poop".