have nothing between the/(one's) ears

have nothing between the/(one's) ears

To be rather stupid, dull, or dimwitted; to not have much common sense or basic intelligence. The expression is a way of saying that one has no brain. She seems nice enough, but I get the sense that she has nothing between her ears. Jake always goes out with really attractive guys that have nothing between the ears.
See also: between, ear, have, nothing
Farlex Dictionary of Idioms.
See also:
  • be not much between the ears
  • not have much between the ears
  • be (as) thick as a brick
  • mouth-breathing
  • be (as) thick as a short plank