The phosphorescent coating inside the screen of a cathode-ray tube.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "phosphor" in a sentence
"Some of you (assuming there is a "you" out there in phosphor land) may have read the FIRESTAR 4-book trilogy."
"The answer lies in a chemical powder called phosphor, which is sprayed against the inner surface of the glass tube."
"And the lamp tube is usually coated with a man made fluorescent powder frequently called a phosphor, but there is no phosphor in the powder coating."