he has a screw loose
Preserved but no longer current.
Era: ca. 1898 (Victorian)
Sources & notes
Reproduced from Brewer’s Dictionary of Phrase and Fable (1898 edition, public domain; archive.org, retrieved 2026-07-31; OCR text, minor errors possible). Reflects the scholarship and attitudes of its era.
Common questions
What does “he has a screw loose” mean?
He is not quite compos mentis, he's a little mad. His mind is like a piece of machinery that needs adjusting — it won't work properly.
Is “he has a screw loose” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.