1. A person that speaks without moving their bottom jaw to express themselves for fear that the corn cob will fall out of their ass.
2. (noun) an incredibly annoying, privileged and clueless person. Usually white, but there are many exceptions.
3. a cracker
"I'm sick of Diddy changing his name every fuckin' year and throwin' his damned all white parties. He's so lock jaw.
White: See Thurston Howell III of Gilligan's Island.
Non-white: See Hilary and Carlton Banks on the Fresh Prince Of Bel-Air.