wag (one's) chin
To talk or chat, especially idly or at length. A less-common variant of "wag one's tongue." My dad is usually a pretty quiet guy, but get him talking about electrical engineering and he can wag his chin for hours at a time. My wife and her sister haven't seen each other in a while, so they've been wagging their chins all afternoon.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
wag one's chin
Rur. to talk. She loves to visit. She'll wag her chin for hours. He was on the phone, wagging his chin to his buddy.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.