know-it-all

from WordNet (r) 3.0 (2006)

know-it-all
    n 1: someone who thinks he knows everything and refuses to
         accept advice or information from others [syn: {know-it-
         all}, {know-all}]

from The Collaborative International Dictionary of English v.0.48

Know-it-all \Know"-it-all`\, n.
   One who knows everything; hence, 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. [Colloq. & pejorative]

   Note: the use of this term implies that the speaker
         disapproves of this behavior, and may think that it is
         unjustified
         [1913 Webster +PJC]

from Moby Thesaurus II by Grady Ward, 1.0

38 Moby Thesaurus words for "know-it-all":
      Narcissus, aggressively self-confident, biggety, braggart,
      bumptious, chesty, cocky, conceited, egocentric, egoist, egotist,
      immodest, individualist, narcissist, narcist, no modest violet,
      obtrusive, overwise, peacockish, peacocky, perk, perky, pert,
      puffed up, self-conceited, self-opinionated, smart aleck,
      smart-alecky, smarty, smarty-pants, stuck-up, swelled-headed,
      swellhead, wise guy, wiseacre, wisecracker, wisehead,
      wisenheimer