whiten

from The American Heritage® Dictionary of the English Language, 5th Edition.

• transitive & intransitive verb To make or become white or whiter, especially by bleaching.

from The Century Dictionary.

• To become white; turn white; bleach: as, the sea whitens with foam.
• To make white; bleach; blanch; whitewash: as, to whiten cloth; to whiten a wall.
• Synonyms Whiten, Bleach, Blanch, Etiolate. Whiten may be a general word for making white, but is chiefly used for the putting of a white coating upon a surface: as, a wall whitened by the application of lime; the sea, whitened by the wind. White for whiten is old-fashioned or Biblical. Bleach and blanch express the act of making white by removal, change, or destruction of color. Bleaching is done chemically or by exposure to light and air: as, to bleach linen or bones. Blanching is a natural process: celery and other plants are blanched or etiolated by excluding light from them; cheeks are blanched by fear, when the blood retires from their capillaries and leaves them pale. See also defs. 5 and 6 under blanch.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To make white; to bleach; to blanch; to whitewash.
• intransitive verb To grow white; to turn or become white or whiter

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• verb transitive To make white or whiter; to bleach or blanch.
• verb intransitive To become white or whiter; to bleach or blanch.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb turn white