a few cards short of a (full) deck

a few cards short of a (full) deck

A derogatory phrase meaning not very intelligent or of questionable mental capacity. It can appear in many different forms and variations (for example: a few sandwiches shy of a picnic, one card shy of a full deck, etc.). He says he's going to start a business selling bees as pets—I think he may be a few cards short of a full deck. The new manager is nice enough, but he's a few cards short of a deck, if you ask me.
See also: card, deck, few, of, short
Farlex Dictionary of Idioms.
See also:
  • a few cards shy of a (full) deck
  • a few eggs short of a dozen
  • bananas
  • a few bananas short of a bunch
  • be a waste of space
  • carry a Chinaman on (one's) back
  • have a Chinaman at (one's) neck
  • have a Chinaman on (one's) back
  • Chinaman's chance
  • Chinaman's chance, he hasn't a/not a