It looks like a normal, cecal, poop. They do it every 8-10 poops, and it stinks like nothing else. Chickens intestines have two, kind of pouches, that's called the caecum. Bacteria in those "pouches" helps digest particularly tough, fibrous bits of food. It's so they can extract all the nutrients possible out of that food. Unfortunately, when it stays in there that long, it makes for a stinking mess when it finally comes out.
