once in a blue moon

American  

[wuhns in uh bloo moon] / ˈwʌns ɪn ə ˈblu ˈmun /

idiom

1. blue moon.

---

once in a blue moon Cultural  

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.

---

once in a blue moon More Idioms  

1. 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]

---

Etymology

Origin of once in a blue moon

First recorded in 1830–40

Example Sentences

Kovacic's 64th-minute strike against Luton was one of those goals you see a defensive midfield player score once in a blue moon - no pun intended.

From BBC • Apr. 15, 2024

“I drive that car maybe once in a blue moon and I loved that car.”

From Washington Times • May 22, 2023

So their metabolism must allow them to store energy to persist long periods without food, then release energy to swim against strong currents once in a blue moon.

From Scientific American • Feb. 24, 2023

While this isn't a huge problem when done once in a blue moon, storing wet or dirty shears and knives over time will start taking its toll…mostly in the name of rust.

From Salon • May 8, 2022

“Not once in a blue moon, or a month of Sundays.”

From "The Graveyard Book" by Neil Gaiman

Related Words

• every now and then
• every so often
• infrequently
• intermittently
• now and again
• occasionally
• periodically
• sporadically