Source : Webster's Revised Unabridged Dictionary (1913)

Beau \Beau\, n.; pl. F. {Beaux} (E. pron. b?z), E. {Beaus}. [F.,
   a fop, fr. beau fine, beautiful, fr. L. bellus pretty, fine,
   for bonulus, dim. of bonus good. See {Bounty}, and cf.
   {Belle}, {Beauty}.]
   1. A man who takes great care to dress in the latest fashion;
      a dandy.

   2. A man who escorts, or pays attentions to, a lady; an
      escort; a lover.

Source : WordNet®

beau
     n 1: a man who is the lover of a girl or young woman; "if I'd
          known he was her boyfriend I wouldn't have asked" [syn:
          {boyfriend}, {fellow}, {swain}, {young man}]
     2: a man who is much concerned with his dress and appearance
        [syn: {dandy}, {dude}, {fop}, {gallant}, {sheik}, {swell},
         {fashion plate}, {clotheshorse}]
     [also: {beaux} (pl)]