Faux-it-all
n. A person who talks like they know everything, when in reality they have no idea what they're talking about. A fake know-it-all.
Paul talks out of his ass all the time, then gets super defensive when you call him on his bullshit. Then he just keeps talking and talking. He puts his two cents in every conversation and he's always wrong but will never admit it. He's SUCH a faux-it-all.