A popinjay is a self-centered chatterbox. The word popinjay isn't used much these days, which is too bad — it could describe plenty of people who talk too much.
A popinjay is a person who's both talkative and cocky, who struts around chattering like a parrot. Fittingly, it's also an old-fashioned word meaning parrot, and the name of a sport also known as pole archery, in which players shoot at wooden bird shapes with either rifles or crossbows. The origin of popinjay is unknown, but one guess is that its roots are imitative, meant to sound like the cry of a bird.