out of the blue
Meaning
Suddenly and unexpectedly, without warning or an obvious cause.
Origin
The phrase alludes to something appearing from a clear blue sky—i.e., without any sign it was coming. It became common in modern English to mean “unexpectedly.”
Notes
Emphasizes surprise and lack of warning; often neutral or mildly negative (caught off guard). Used for events, messages, ideas, or visits. Works in both informal and formal contexts.
Examples
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Out of the blue, my old college roommate called to apologize.
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The company announced layoffs out of the blue, and everyone was stunned.
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She showed up at the party out of the blue, even though no one invited her.
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Out of the blue, it started pouring, and we had to run for cover.
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He proposed out of the blue during a quiet walk in the park.
Grammar & Usage Notes
Usually an adverbial phrase: “happen/appear/come out of the blue.” Often with “come/call/email/text out of the blue.” Can modify clauses (“Out of the blue, …”).
Synonyms
- suddenly
- unexpectedly
- without warning
- all of a sudden
- out of nowhere
Antonyms
- as expected
- predictably
- with warning
- gradually