[syn: widening, broadening]
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]
WordNet (r) 3.0 (2006):
broadening
    n 1: the act of making something wider [syn: widening,
         broadening] [ant: narrowing]
    2: the action of making broader; "the broadening of travel"
    3: an increase in width [syn: widening, broadening] [ant:
       narrowing]