1. Someone prone to talking a lot or at length. Good luck getting out of here—Aunt Louise is a real flapjaw and could easily blather to you for an hour.
2. Someone who too readily shares information, especially that which is private or confidential. Some flapjaw has been talking to the press about our new product. Needless to say, if I find out who it is, they will be fired on the spot. If you've got a secret, don't tell it to a flapjaw like Marty!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
1. n. a talkative person. Martin is anything but a flapjaw. I bet he doesn’t say a dozen words per hour.
2. n. chatter; gossip. Too much flapjaw for me to concentrate in here.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.