flap your gums
flap (one's) gums
To chatter or blather. Quit flapping your gums—I need some quiet so I can think! Whenever Charlie starts to flap his gums, I can't get in a word!
flap your gumsAMERICAN, INFORMAL
If someone flaps their gums, they talk a lot without saying anything important. Who wants to hear you flapping your gums first thing in the morning?