Source : Webster's Revised Unabridged Dictionary (1913)

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.

         The broadening sun appears.              --Wordsworth.

Broaden \Broad"en\, v. t.
   To make broad or broader; to render more broad or
   comprehensive.

Source : WordNet®

broaden
     v 1: make broader; "broaden the road"
     2: extend in scope or range or area; "The law was extended to
        all citizens"; "widen the range of applications"; "broaden
        your horizon"; "Extend your backyard" [syn: {widen}, {extend}]
     3: vary in order to spread risk or to expand; "The company
        diversified" [syn: {diversify}, {branch out}] [ant: {specialize},
         {specialize}]
     4: become broader; "The road broadened"