[1] : The Collaborative International Dictionary of English v.0.48

brighten \bright"en\, v. t. imp.  p. p. brightened; p. pr. 
   vb. n. brightening.

   note: from bright, a.
   1. to make bright or brighter; to make to shine; to increase
      the luster of; to give a brighter hue to.
      1913 webster

   2. to make illustrious, or more distinguished; to add luster
      or splendor to.
      1913 webster

            the present queen would brighten her character, if
            she would exert her authority to instill virtues
            into her people.                      --swift.
      1913 webster

   3. to improve or relieve by dispelling gloom or removing that
      which obscures and darkens; to shed light upon; to make
      cheerful; as, to brighten one's prospects.
      1913 webster

            an ecstasy, which mothers only feel,
            plays round my heart and brightens all my sorrow.
                                                  --philips.
      1913 webster

   4. to make acute or witty; to enliven. --johnson.
      1913 webster
see also:
brightened brightening bright 

[2] : The Collaborative International Dictionary of English v.0.48

brighten \bright"en\, v. i. as. beorhtan.
   to grow bright, or more bright; to become less dark or
   gloomy; to clear up; to become bright or cheerful.
   1913 webster

         and night shall brighten into day.       --n. cotton.
   1913 webster

         and, all his prospects brightening to the last,
         his heaven commences ere world be past.  --goldsmith.
   1913 webster

[3] : WordNet (r) 2.0

brighten
     v 1: make lighter or brighter; "the paint will brighten the room"
          syn: lighten up, lighten ant: darken
     2: become clear; "the sky cleared after the storm" syn: clear
        up, clear, light up ant: overcast
     3: become brighter; "the sky brightened around noon"; "her face
        brightened when she heard the good news" ant: darken
     4: become brighter; "the sky brightened" syn: lighten ant:
         darken
see also:
lighten up lighten darken clear up clear light up 
overcast 

[4] : Moby Thesaurus II by Grady Ward, 1.0

51 moby thesaurus words for "brighten":
   animate, beacon, boost, break, brighten up, buoy up, burnish,
   cheer, cheer up, dawn, encourage, enlighten, enliven, exhilarate,
   flood with light, floodlight, gild, gild the lily, give a lift,
   gladden, grow bright, grow light, hearten, highlight, illume,
   illuminate, illumine, inspire, inspirit, invigorate, irradiate,
   light, light up, lighten, liven, luminate, overshine, perk up,
   pick up, polish, rejoice, rejoice the heart, relume, relumine,
   shed light upon, shine, shine upon, spotlight, sweeten,
   throw light upon, vitalize

Brighten >> B Words
Brighten, definition of term: Brighten
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