Meaning of double refraction

dou'ble refrac'tion

Pronunciation: [key]
— Optics. Optics.
  1. the separation of a ray of light into two unequally refracted, plane-polarized rays of orthogonal polarizations, occurring in crystals in which the velocity of light rays is not the same in all directions. Also called
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.