2. Someone who is acting stupid, dumb, lame, annoying, etc.
3. An insult.
Person B: I'm not feelin so hot and idk why.
Person A: You have pooptartitis.
2. Person 1: Watch Ben, he's about to do something really stupid!
Person 2: Ben is such a pooptart!
3. Don't look at me like that, you little pooptart!