The Collaborative International Dictionary of English v.0.48:

Hotshot \Hot"shot`\, n.
   a successful, self-confident person who is regarded by others
   as highly skilled; -- sometimes used ironically in reference
   to aggressive persons whose opinion of their own talents is
   considered exaggerated.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

hotshot \hot"shot`\, a.
   1. highly talented, self-confident and successful.
      [PJC]

   2. flamboyantly displaying one's skills.
      [PJC]

WordNet (r) 3.0 (2006):

hotshot
    n 1: someone who is dazzlingly skilled in any field [syn: ace,
         adept, champion, sensation, maven, mavin,
         virtuoso, genius, hotshot, star, superstar,
         whiz, whizz, wizard, wiz]