blue moon

[ bloo-moon ]
See synonyms for blue moon on Thesaurus.com
noun
  1. a second full moon in a month, occurring every two to three years as a result of the discrepancy between a lunar year and a solar year.

  2. (formerly) the third full moon in a season with four full moons instead of the usual three.

  1. a long, indeterminate stretch of time, as between occurrences of a rare event or phenomenon.

  2. an uncommon phenomenon in which the moon appears to have a blue tinge because of the filtering effect of smoke or dust particles in the atmosphere.

idiom
  1. a very long period of time: Such a chance comes once in a blue moon.

Origin of blue moon

1
First recorded in 1815–25

Words Nearby blue moon

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

How to use blue moon in a sentence

  • As a brand, blue moon beer is not unlike Blue Dog Democrats, walking the tightrope of competing identities.

    The Beer Summit | Mark Katz | July 28, 2009 | THE DAILY BEAST
  • But conductors are no more infallible than other people, and once in a blue moon in going through a train they miss a passenger.

    The Wreckers | Francis Lynde
  • "A purple sea, a blue moon, and a red fish—it looks crazy to me," muttered the old agent.

    Through the Wall | Cleveland Moffett
  • He was seated beside the great, wood-burning stove in the great front room of the blue moon.

    Red Dynamite | Roy J. Snell
  • When they gathered in the back room of the blue moon, the players found a blackboard hung upon the wall.

    Red Dynamite | Roy J. Snell
  • And a mighty horde in trucks, busses, and private cars, some even on bicycles was pouring toward the blue moon at sunset.

    Red Dynamite | Roy J. Snell

British Dictionary definitions for blue moon

blue moon

noun
  1. the second full moon occurring within a calendar month

  2. once in a blue moon informal very rarely; almost never

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012