GNU Collaborative International Dictionary of English

Found one definition

1.       
   Whiten (?), v. i. [imp. & p. p. Whitened (?); p. pr. & vb. n. Whitening.] [OE. whitenen; cf. Icel. hvītna.] To grow white; to turn or become white or whiter; as, “the hair whitens with age; the sea whitens with foam; the trees in spring whiten with blossoms.”
   
   [1913 Webster]