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View synonyms for once in a blue moon

once in a blue moon

[ wuhns in uh bloo moon ]

once in a blue moon

  1. To do something “once in a blue moon” is to do it very rarely: “That company puts on a good performance only once in a blue moon.” The phrase refers to the appearance of a second full moon within a calendar month, which actually happens about every thirty-two months.


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Word History and Origins

Origin of once in a blue moon1

First recorded in 1830–40
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Idioms and Phrases

Rarely, once in a very long time, as in We only see our daughter once in a blue moon . This term is something of a misnomer, because an actual blue moon—that is, the appearance of a second full moon in the same calendar month—occurs every 32 months or so. Further, the moon can appear blue in color at any time, depending on weather conditions. [Early 1800s]

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Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.

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Once bitten, twice shyonce in a lifetime