the lights are on, but nobody's home

the lights are on, but nobody's home

A humorous expression used to say that someone is stupid, unthinking, or inattentive. Hello, Pete? Earth to Pete. He must be daydreaming again—the lights are on, but no one's home. I kept asking the suspect questions about what happened, and they just kept staring at me blankly. The lights are on, but no one's home, you know what I mean?
See also: but, home, lights
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

the lights are on but nobody's home

or

the lights are on but no one's home

INFORMAL
If you say of someone that the lights are on but nobody's home, you mean that they are stupid or not reacting to what is happening. When I tell them anything, they look at me like the lights are on but nobody's home.
See also: but, home, lights, on
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012

the lights are on but no one is at home

used to refer sardonically to someone of limited mental capacity.
See also: but, home, lights, no, on, one
Farlex Partner Idioms Dictionary © Farlex 2017

the lights are ˈon but nobody’s ˈhome

(saying, humorous) used to describe somebody who is stupid, not thinking clearly or not paying attention: Don’t try discussing anything intelligent with Alice. The lights are on but nobody’s home, I’m afraid.
See also: but, home, lights, on
Farlex Partner Idioms Dictionary © Farlex 2017
See also: