1. Persistent emission of light following exposure to and removal of incident radiation.
2. Emission of light without burning or by very slow burning without appreciable heat, as from the slow oxidation of phosphorous: "He saw the phosphorescence of the Gulf weed in the water" (Ernest Hemingway).

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.