1. speak convincingly about your ability to do something
he talks a big game, but can't back it up
To ‘talk a big game’ or ‘talk a good game’ means to talk convincingly about your abilities or make people believe things about you that are often false or overstated. The implication with ‘you talk a big game’ is that you don’t really believe what the person is telling you. This is a very casual expression best suited to social situations but you may hear it in professional contexts also.