WordWeb Online

1. Marked by casual disrespect
   "the student was kept in for insolent behaviour";
   - impudent, snotty-nosed, flip
    
2. Unrestrained by convention or propriety
   "the modern world with its quick material successes and insolent belief in the boundless possibilities of progress";
   - audacious, barefaced, bodacious [N. Amer, informal], bald-faced, brassy, brazen, brazen-faced

See also: disrespectful, unashamed

Encyclopedia: Insolent