Answer: knowall

AnswerCrossword Clue
KNOWALL

Smarty-pants

KNOWALL

Insufferable type

KNOWALL

It's impossible to argue with one

KNOWALL
One claiming to have the answers
KNOWALL
Boaster of brainpower
KNOWALLWise guy?
KNOWALLWiseacre
KNOWALLOne with omniscience
KNOWALLHe thinks he has the answers