Information without context, memorizing without learning, knowing without understanding. Dumb knowledge is only useful in very limited areas. Memorizing all of the airport codes of the world would be helpful to me, but would say nothing about my intelligence AND would not help me tell a client whether it would be best for them to fly through Narita or Kansai. Many so-called smart people get through life on dumb knowledge; many truly smart people (especially in high school and college) use dumb knowledge to make themselves sound smart, bludgeoning the listener with trivia and meaningless statistics, or spieling off stupid programming tricks without any sort of holistic grasp of the larger picture. Dumb knowledge of a subject is more the opposite of grokking something than is knowing nothing at all.