English · Daily Life
once in a blue moon
/wʌns ɪn ə bluː muːn/
[/wʌns ɪn ə bluː muːn/]
very rarely
Intermediatephrase
Definition
Very rarely; almost never.
Example
We only see our cousins once in a blue moon, since they live on the other side of the world.
We only see our cousins once in a blue moon, since they live on the other side of the world.
Etymology
A 'blue moon' is a rare second full moon in a month; the phrase dates to the 19th century.
How & Where It’s Used
Informal and common for describing rare events.