once in a blue moon
Very rarely; very infrequently.
Meaning adapted from Wiktionary, available under CC BY-SA 4.0.
“We only eat out once in a blue moon.”
“My brother lives abroad, so I see him once in a blue moon.”
“Now that they both have demanding jobs and young children, the old friends manage to meet only once in a blue moon.”
first recorded 16th c. disputed origin
'Blue moon' meant something absurd or never in the 16th century ('if they say the moon is blue, we must believe it is true', 1528); later attached to the rare second full moon in a calendar month.
- 01
all at once
Unexpectedly; without warning; all of a sudden.
- 02
ask for the moon
To claim or desire something that one cannot have.
- 03
blue chamber
A forbidden room.
- 04
blue devils
Low spirits; depression.
- 05
blue moon
A long time.
- 06
blue note
The flatted 5th scale degree in the blues scale.
- 07
blue ribbon
Highly superior in quality, style, substance, prestige, etc.
- 08
blue state
A state of the United States voting Democratic in a given election, or tending to vote Democratic in general.
Last updated August 10, 2026