moonbow

noun

1. A rainbow formed by moonlight diffracted by water droplets in the air, usually fainter than a daytime rainbow and with fewer distinguishable colours.

   “Often rainbows by night or moonbows span the lake.”

   “Among the rarer optical effects associated with the moon are also moonbows or lunar rainbows.”

   “When the sun shines over Kentucky's Cumberland Falls, the mist creates a rainbow on most days. If the moon shines brightly enough, it can create a moonbow, too!”