talk through (one's) arse
1. vulgar slang To say foolish things; to talk of nonsense. Primarily heard in UK. Don't pay Jonathan any mind, Mary, he's just talking through his arse again.
2. vulgar slang To exaggerate one's achievements or knowledge of some subject; to bluff or boast. Primarily heard in UK. Dorothy keeps saying she can outrun anyone in our school, but she's talking through her arse if you ask me. It seemed like the candidate was talking through his arse for a while when the debate turned to the topic of tax policy and law.