The small metal implements that hang on your keyring to lock and unlock your vehicle. also used when some non driving hick parks too close to your car and you, in a fit of rage, need to reach for your sharpest key and scrape the shit out of that car.
Key is the new word at Girls High school. It's the new cool, and mint. I know that it's usual meaning is an object used to unlock doors. But no! It is the newest slang for cool.