To leave a group of friends, social gathering, or other such event with little or no warning or reason why. To bail.
Dude, I can't believe you're bailing already. It's not even midnight!
To purposely or accidentally not land a trick, such as a grind, grab, air, gap, spin, or flip. Term should only be used when referring to extreme sports with wheels, such as skateboarding, rollerblading, BMXing, and scootering.
"Damn skateboarders. Bailing all their tricks."