You think you're so smart!

You think you're so smart!

Inf. You act as if you know far more than you do. (Also with subjects other than second person.) You think you're so smart! You don't know anything! Boy! He thinks he's so smart!
See also: think
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • as we know it
  • AFAIK
  • before you know it
  • a closed book
  • closed book, a
  • I know
  • can't say as I do
  • (I) can't say as I do
  • know where it's at
  • before you know where you are