When you have a teacher who is a complete and utter bastard. Derived from the word dick head or Kunt, which both have the same meaning.
Boy 1: Ohh shit man, look who is our sub this lesson!
Boy 2: Fuck, its one of those dickhead teachers who think they are so smart. He was probably beaten as a child too :P
Boy 1: This gits such a Patelle!