Similar word to irreverential:

aweless, cheeky, cocky, contemptuous, crusty, derisive, flip, flippant, fresh, iconoclastic, impertinent, impious, impudent, insolent, irreverential, mocking, out-of-line, profane, rude, sacrilegious, sassy, saucy, tongue-in-cheek, ungodly, unhallowed, unholy