blue moon

noun

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

Synonyms

• aeon
• eon
• age
• coon's age
• cycle
• donkey's years [chiefly British]
• eternity
• forever
• long
• months
• moon

Examples of blue moon in a Sentence

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

Recent Examples on the Web

Their version of Superman was made with blue moon, red pop and lemon flavors. —Jalen Williams, Detroit Free Press, 22 Dec. 2024

August is for Astronomy lovers:A rare, seasonal blue moon is coming, and the sky in August has more surprises in store John Tufts covers trending news for IndyStar and Midwest Connect. —John Tufts, The Indianapolis Star, 8 Aug. 2024

There are also two types of blue moons: monthly and seasonal. —Joyce Orlando, The Tennessean, 8 Aug. 2024

The last seasonal blue moon was in August 2021, and the next one won't occur until May 2027. —Tiffany Acosta, The Arizona Republic, 16 Aug. 2024

Word History

First Known Use

1821, in the meaning defined at sense 1