One who has/thinks they have a great deal of knowledge, but grossly overuses it.
Someone who, at a party, always finds people walking away from them muttering " What a loser. Doesn't he have anything better to do?" after quoting useless and/or inaccurate statistics to make him look more interesting.
A person that uses their knowledge/feigned knowledge to make someone feel inferior for no other reason than to feel intellectually superior.
Man at a party: "Discount our neighbors to the east and I think you'll find we've got a sleeping giant on our hands. A veritable sleeping giant."
Everyone else at the party: "What a loser. He is so mentally obese that there should be a Richard Simmons work out tape dedicated to him."