be talking through your hat
be talking through (one's) hat
1. To be saying foolish things; to be talking nonsense. Don't pay Jonathan any mind, Mary, he's just talking through his hat again.
2. To be exaggerating one's achievements or knowledge of some subject; to be bluffing or boasting. Dorothy keeps saying she can outrun anyone in our school, but she's talking through her hat if you ask me. It seemed like the candidate was talking through his hat for a while when the debate turned to the topic of tax policy and law.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
be talking through your hatINFORMAL
If someone is talking through their hat, what they are saying is silly or totally incorrect. Mrs Smith had told Adam he was talking through his hat if he thought communism would work. Quite honestly, I think he was talking through his hat.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012