Beating The Gun

An early 1950s film noir, in which a hard-bitten L.A. cop, played by an aging Humprey Bogart, investigates the death of an Olympic sprinter, who is killed when someone replaces a starter pistol with a real gun.

Okay...actually, its slang term used when a trader is able to properly time the market.

You own stock in a company that most people have never heard of, but which has a big contract to provide plastic cup holders for a large car manufacturer. News breaks that the auto maker had terrible sales for most recent quarter. You immediately know that the price of your shares will eventually tank, since bad sales for the automaker means bad sales for the cup holder company. You quickly sell your shares before most of the rest of the market figures out the connection between the two companies. You just beat the gun.

There's a distinction here between beating the gun and insider trading. Insider trading is making moves before the general market because you are illegally using non-public information. Beating the gun is just timing the market well by quickly reacting to events.