WordWeb Online

1. Showing lack of due respect or veneration
   "irreverent scholars mocking sacred things"; "noisy irreverent tourists"
    
2. Lively and humorously cheeky or forward
   "a certain irreverent gaiety and ease of manner";
   - impertinent, pert, saucy [informal], cheeky [Brit, informal]
    
3. Not revering god
   "I know a fair amount of atheists, seeing as I live in a relatively irreverent town";
   - godless

See also: aweless, awless, blasphemous, disrespectful, impious, profane, sacrilegious, spirited

Antonym: reverent

Encyclopedia: Irreverent