To grow bright or more bright; become less dark or gloomy: literally or figuratively.To make bright or brighter in any manner; shed light on; make to shine; increase the luster of.To dispel gloom from; cheer; make gay or cheerful: as, to brighten prospects.To make illustrious or more distinguished; heighten the splendor of; add luster to.To make acute or witty; sharpen the faculties of.To add brilliancy to the colors of (prints, etc.), by boiling them in a solution of soda.