3. The actual toilet.
The pooper is clogged. See - Shitter, Crapper, Toilet
4. A word for small children, as they don't do a lot more than eat, sleep, and poop.
How's the little pooper doing? See - Crothling, Womb Lice, Cocksmurf
5. A mild oath for something bad that has happened.
How was your day?
It was a real pooper. See - Pisser, Bitch, Clusterfuck