What is an overhook in BJJ?

An overhook (or whizzer) wraps your arm over your opponent's arm and pulls it tight to your body, controlling their arm from outside. Overhooks counter underhooks and defend takedowns - when someone shoots, you can whizzer to stop their penetration and spin behind them. From guard, overhooks control posture and set up triangles, omoplatas, and sweeps. The overhook is defensive but creates offensive opportunities. Use it to neutralize someone who wins the underhook battle. Key detail: really clamp down and pull their arm tight to your ribs; a loose overhook does nothing.