be one sandwich short of a picnic

be one sandwich short of a picnic

To be not very intelligent or of questionable mental capacity. It can appear in many different forms and variations (for example: a few bricks shy of a load, a few cards shy of a full deck, etc.) He says he's going to start a business selling bees as pets. I think he may be one sandwich short of a picnic.
See also: of, one, picnic, sandwich, short
Farlex Dictionary of Idioms.
See also:
  • be one brick short of a (full) load
  • be one card short of a full deck
  • be one card shy of a (full) deck
  • be several bricks short of a (full) load
  • be several cards short of a (full) deck
  • be several cards short of a full deck
  • a brick short of a load
  • a few cards short of a (full) deck
  • a few cards shy of a (full) deck
  • two bricks shy of a (full) load