Answer: knowall

AnswerCrossword Clue
KNOWALLSmarty-pants
KNOWALLInsufferable type
KNOWALLIt's impossible to argue with one
KNOWALLOne claiming to have the answers
KNOWALLBoaster of brainpower
KNOWALLWise guy?
KNOWALLWiseacre
KNOWALLOne with omniscience
KNOWALLHe thinks he has the answers