The Collaborative International Dictionary of English v.0.48:

Broaden \Broad"en\, v. t. [imp. & p. p. Broadened; p. pr. &
   vb. n. Broadening.] [From Broad, a.]
   To grow broad; to become broader or wider.
   [1913 Webster]

         The broadening sun appears.              --Wordsworth.
   [1913 Webster]