The tip of a piece of poo which pokes out of the water in the toilet bowl, like an iceberg in the ocean. But only this is poo, not ice. That is why it is called a poo berg.

v. collectively or individually finding someone/something to blame for a problem, as opposed to brainstorming which connotes finding solutions to a problem

n. the act of finding someone/something to blame for a problem

(from a TV ad for HD television)

When you poo so much that some of the poo comes out of the water in the toilet. That is a pooberg