'Bigwig' definitions:

Definition of 'bigwig'

noun

The most important person in a group or undertaking [syn: kingpin, top banana, bigwig]

From: GCIDE

Bigwig \Big"wig`\, n. [Big,a.+ wig.] A person of consequence; as, the bigwigs of society. [Jocose] [1913 Webster]
In our youth we have heard him spoken of by the bigwigs with extreme condescension. --Dickens. [1913 Webster]