have a screw loose

Idioms  

1. Be mentally unstable or eccentric, as in Anyone who approves that purchase must have a screw loose. This term likens a mental weakness to a machine in which a part is not securely fastened. An antonym is have one's head screwed on right; for example, She's very capable; she has her head screwed on right. [Slang; early 1800s]

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Example Sentences

“Everyone in speedskating recognizes that Eric Heiden is the greatest speedskater who ever lived. Even saying, ‘Yeah, we should try that,’ that’s like saying, ‘Do you have a screw loose or something?’

From Washington Times

But, Mr Cummings tells the BBC that anyone who says they are sure, five years after the result, that Brexit is a good thing must "have a screw loose".

From BBC

“You are either incompetent or for some reason you have a screw loose and you want to have open borders.”

From Washington Times

Wlodzimierz Lipa, a 71-year-old pensioner who got his second Pfizer shot last week in Walbrzych, said that people attacking the mayor as a Nazi “have a screw loose.”

From New York Times

“He said, ‘You kind of have to have a screw loose to do this,’” Wood said.

From Washington Times