blue moon

English

Noun

a blue moon (plural blue moons)

1. (rare) The moon tinted towards blue as it appears in the sky, caused by dust or smoke in the atmosphere.
2. (archaic) Something absurd.
   • 1528, Rede Me and Be Not Wrothe, pamphlet

     Yf they say the mone is belewe, we must believe that it is true.

3. (obsolete) The third full moon in a quarter that contains four rather than the usual three full moons.
4. (idiomatic) (by extension) A long time.
5. A flavor of sweet ice cream that is popular in the Midwestern U.S. and is a component of Superman ice cream.
   • Blue Moon (ice cream) on Wikipedia.Wikipedia:Blue Moon (ice cream)

Etymology

Mistake in Sky & Telescope magazine in 1946, retracted nearly 60 years later.

Noun

Wikipedia

a blue moon

1. The second of two full moons that occur in the same calendar month.

Derived terms

• once in a blue moon