with a loose screw

with a loose screw

Having or characterized by silliness, eccentricity, craziness, or mental instability. There's some guy with a loose screw standing on the corner yelling obscenities at passersby. I have this strange fear that I'm going to turn into a lonely old bachelor with a loose screw when I get old.
See also: loose, screw
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
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