Once in a blue moon

Meaning: Very rarely.

Language: English

Literally: Once in a blue moon

Category: Nature

Origin: A 'blue moon' is a rare second full moon in a month; the phrase fixed the sense of rarity by the 19th century.

Equivalents in other languages

More idioms — Nature

More English idioms

From our compliments & insults

Browse all compliments & insults →

← Back to Idioms