Source : Webster's Revised Unabridged Dictionary (1913)

Cocksure \Cock"sure`\, a.
   1. Perfectly safe. [Obs.]

            We steal as in a castle, cocksure: . . . we walk
            invisible.                            --Shak.

   2. Quite certain. [Colloq.]

            I thought myself cocksure of the horse which he
            readily promised me.                  --Pope.

Source : WordNet®

cocksure
     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: {overconfident}, {positive}]