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Meaning of brightener

bright•en•er

Pronunciation: (brīt'n-ur), [key]
— n.
  1. a person or thing that brightens.
  2. a chemical or other agent used to increase brightness, as one added to toothpaste or detergent to intensify the cleansing or bleaching process.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.