all mouth and trousers
Full of boastful, arrogant, or shallow talk, usually by a male, who then cannot deliver on his claims. The variant form, "all mouth and no trousers" (meaning the same), is also often used. Primarily heard in UK. I find that most of the men in the city are all mouth and trousers. They all act like they are God's gift to women, but I've yet to meet one who's at all interesting. The opposition party is all mouth and trousers, for they have no real plan to address the things they are criticizing.