moonbow

/ˈmunˌboʊ/
noun
  1. A rainbow caused by the light of the moon, usually appearing as a white or faintly colored arc in the night sky.
    • The photographer captured a stunning moonbow arching across the dark sky.
    • We stayed up late hoping to see a moonbow over the waterfall.
    • Moonbows are much rarer than rainbows because they need a bright moon and misty air.