If you say that someone is all mouth and no trousers, you mean that they often say they are going to do something impressive or exciting but never actually do it. Ahmed's failure to bid for either company has left him with a reputation for being all mouth and no trousers. Note: Less commonly, people use all mouth and trousers with the same meaning. He was a fast-talking, London media type, all mouth and trousers. Note: Sometimes people use another noun instead of trousers. He says he's going to do something about it but he never will. He's all mouth and no action. Note: Sometimes people just say that someone is all mouth. I wouldn't worry about James — he's all mouth.