Source : Webster's Revised Unabridged Dictionary (1913)

Bigwig \Big"wig`\, n. [Big,a.+ wig.]
   A person of consequence; as, the bigwigs of society. [Jocose]

         In our youth we have heard him spoken of by the bigwigs
         with extreme condescension.              --Dickens.

Source : WordNet®

bigwig
     n : the most important person in a group or undertaking [syn: {kingpin},
          {top banana}]