The Oxford Thesaurus An A-Z Dictionary of Synonyms - overconfidentadj.

1) brash, arrogant, cocksure, cocky, brazen, hubristic, swaggering, audacious, overbearing, vainglorious, Colloq pushy: It is harmful for a sportsman's morale to be overconfident of winning. 2) heedless, foolhardy, thoughtless, short-sighted, hasty: Rock-climbers should not be overconfident and rely entirely on their ropes.