lip flappin'

When you've just told someone something they don't appreciate (e.g. insulted them, their family, or anything else in general) and they're getting all exasperated, and are trying to think of something to yell at you, but their brains aren't as quick as their mouth, so their lips start moving around just gettin' ready for the words with their facial expression still shocked.

So, I called her a dumbass, and I was doing really well at keeping my laughter in check, until she started lip flappin'.

lip flappin' by TipsFromTheHelpDesk September 5, 2017

Excessive Lip Flappin' 

Usually describes a pesron who talks too much, whether about themselves or about alot of useless shit nobody wants to hear.

I wish that nigga would shut tha fuck up with all that Excessive Lip Flappin'! Nobody cares how big you think you are!

Excessive Lip Flappin' by Westside Digital Pimp April 16, 2022

lip-flapping 

1. When a guy eats a girl out.

2. When a guy plays with the "lips" of a girls vagina.

Dude, I was lip-flapping with Susan last night, it was hot.

lip-flapping by Jake Demeter August 16, 2011