nothing upstairs
Not very much in the way of intelligence. She seems nice enough, but I get the sense that there's nothing upstairs. Jake's boyfriend is incredibly attractive, but he has nothing upstairs from what I can tell.
nothing upstairs
Fig. no brains; stupid. Tom is sort of stupid. You know—nothing upstairs. I know what's wrong with you. Nothing upstairs.
nothing upstairs
phr. no brains; stupid. Tom is sort of stupid acting. You know—nothing upstairs. I know what’s wrong with you. Nothing upstairs.