n. The optical phenomenon in some colored, transparent crystals (such as tourmaline) in which the color is different in different directions.
the GNU version of the Collaborative International Dictionary of English
n. The property possessed by some crystals, of showing different colors when viewed in the direction of different axes.
The Century Dictionary and Cyclopedia
n. In crystallography, the variation in color observed in some crystals when viewed in different directions, due to the fact that the rays having vibrations in different planes suffer absorption in different degrees.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. the phenomenon of different colors appearing when certain crystals are viewed from different directions
Word Usage
"Such an effect is called pleochroism, and crystals which show variations in their colour when viewed from different angles, or by transmitted light, are called pleochroic, or pleochromatic -- from two Greek words signifying "to colour more.""