Definition of out of a or the clear blue sky in English:

out of a (or the) clear blue sky

As a complete surprise: his moods blew up suddenly out of a clear blue sky
More example sentences
  • Aware that such social tornadoes can twist towards them out of a clear sky, governments have learned to be cautious.
  • When angered, people burn, things break and fly around, lightning may strike out of a clear sky.
  • I've heard of lightning coming out of a clear sky.
See parent entry: clear

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Word of the day demoralize
Pronunciation: dəˈmôrəˌlīz
cause (someone) to lose confidence or hope; dispirit