not the sharpest pencil in the cup

not the sharpest pencil in the cup

Not intelligent; dim-witted or prone to stupidity. The new boyfriend isn't the sharpest pencil in the cup, but he's pretty good looking! I wasn't the sharpest pencil in the cup in school, but I still managed to find a profession I loved.
See also: cup, not, pencil, sharp
Farlex Dictionary of Idioms.
See also:
  • not the sharpest tool in the shed
  • not the sharpest knife in the drawer
  • not the sharpest tool in the box
  • smurfbrain
  • airbrain
  • airhead
  • couldn't find (one's) way out of a paper bag
  • out of a paper bag
  • (one's) way out of a paper bag
  • have a thick head