have a screw loose
idiomPart ofloose
have a screw loose — idiom
1. To be slightly strange, foolish, or mentally unstable in a harmless way.
1.idiom
Definition
To be slightly strange, foolish, or mentally unstable in a harmless way.
Example
Anyone who runs a marathon in this heat must have a screw loose.
Quinn's friends joked that she had a screw loose for adopting six cats.