not be all there
be not all there
1. To not be mentally sound. A: "Look at that guy talking to himself on the corner." B: "I reckon he's not all there." My grandfather hasn't been all there for a number of years, which has really had a negative impact on how the kids interact with him.
2. To not be very bright or intelligent; to be dimwitted. Jim's a nice guy, but with some of the foolish things he does, I think he's not all there. My aunt likes to act like she's not all there sometimes, but she's actually incredibly sharp.
not be all thereINFORMAL
If someone is not all there, they are not very intelligent, or are slightly crazy. I tried to talk to her but she wasn't really all there.