a bolt from the blue
Preserved but no longer current.
A sudden and wholly unexpected catastrophe or event, like a "thunderbolt" from the blue sky, or flash of lightning without warning and wholly un- expected. Here "bolt" is used for lightning, though, of course, in strict language, a meteorite, not a flash of lightning, is a thunderbolt.
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 “a bolt from the blue” mean?
A sudden and wholly unexpected catastrophe or event, like a "thunderbolt" from the blue sky, or flash of lightning without warning and wholly un- expected. Here "bolt" is used for lightning, though, of course, in strict language, a meteorite, not a flash of lightning, is a thunderbolt.
Is “a bolt from the blue” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.