1. An abnormal sensitivity to or intolerance of light, especially by the eyes, as may be caused by eye inflammation, lack of pigmentation in the iris, or various diseases.
2. An abnormal or irrational fear of light.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.