Know-it-all
Know-it-all , noun
the use of this term implies that the speaker disapproves of this behavior, and may think that it is unjustified
One who knows everything;
a person who makes pretension to great knowledge, especially one whose didactic conversational habit conspicuously reveals his belief that he has superior knowledge on many subjects; a wiseacre; a know-all; -- usually ironical. [Colloquial & pejorative]