blue moon

noun
|Updated on: 12 Aug 2018

Definition of blue moon

1 : a very long period of time usually used in the phrase once in a blue moon
  • such people happen along only once in a blue moon
  • Saturday Rev.
2 : a second full moon in a calendar month

Examples of blue moon in a Sentence

  1. once in a blue moon we'll get dressed up and eat in a fancy restaurant

Recent Examples of blue moon from the Web

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'blue moon.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of blue moon

1821

in the meaning defined at sense 1

See Words from the same year
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blue moon Synonyms



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