1. become or make black or dark, especially as a result of burning, decay, or bruising: "he set fire to the paper, watching the end blacken as it burned"Similarmake blackblackdarkenmake dark/darkerdirtymake dirtymake sootymake smokystaingrimebegrimebefoulsoilgrow/become blackdarkendimgrow dimcloud overOppositewhitencleanlightenbrighten
▪ dye or color (the face or hair) black for camouflage or cosmetic effect: "in full combat gear with blackened faces"