To place someone's open mouth on a curb and stomp on the top of their head so as to break and/or separate the lower jaw from the upper jaw and breaking teeth in the process.
When you hang out with your friends on the street and there are no chairs so you sit on the curb. Usually done with a 40oz of malt liquor and/or a blunt.
Guy 1: I just want to sit down, relax, smoke this blunt, and sip this 40.
Guy2: shit, looks like we're curb checkin' it.
"Curb" is an acronym for Clean Up Right Behind. No one likes to step in dog poo. So land owners post this sign to to remind you to pick up after your dog.
As Cindy saw the "Curb your dog" sign, she realized she forgot her bags and went home to get them.