Something annoying or difficult to do. British.
Martin's coming over later.
Really? That's guy's a real pain in the pooer.
Someone that is really really EVIL and probably bullies people.
Nicole is such a big pooer, and she hits people.
Yeah, Nicole. You're a BIG POOER!
(n) A person who finds it difficult or impossible to defecate anywhere but a place in which they are comfortable, ie. their own toilet.
Well we can definitely take Nin, she'll poo anywhere. She ain't no comfort pooer!