An inconsiderate asshole who never sits down, who incessantly paces, pounds, and slams their feet into the floor, and lives in the apartment above you.
An exclamation used to express anger when you cannot come up with anything more creative than putting two words together that have nothing to do with each other.
The simple definition is that you are saying "that is really fucking dumb" or something along that line. You cannot use it for obvious stupid things like you can't go to the park because your mom said so, more like your friend is being a bitch and won't let you in their house.
"Jimbo won't let us swim at his house because he's watching his niece again."