Hevelian halo: Meaning and Definition of

He•ve'li•an ha'lo

Pronunciation: (hu-vā'lē-un), [key]
  1. a faint white halo with an angular radius of 90° that is occasionally seen around the sun or the moon, thought to be caused by the reflection and refraction of sunlight by ice crystals.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.