Definitions by Laythem

mouth jerk 

In the Nordic highlands, it was widely though to be rude when prince's of lords would pick their teeth with their fingers in a jerking motion, while speaking ill of their house.

This custom was adopted by the Europeans in the 1600's

When your son is mouthing off, when he should be zipin' the lip. He's being a mouth jerk

mouth jerk by Laythem December 13, 2012