Source : Webster's Revised Unabridged Dictionary (1913)

Overconfident \O"ver*con"fi*dent\, a.
   Confident to excess. -- {O"ver*con"fi*dent*ly}, adv.

Source : WordNet®

overconfident
     adj : marked by excessive confidence; "an arrogant and cocksure
           materialist"; "so overconfident and impudent as to
           speak to the queen"; "the less he knows the more
           positive he gets" [syn: {cocksure}, {positive}]