THE DEFINITION AS EXPLAINED BY BRUCE GRIGGS
Oversteer is a vehicle handling condition where the rear tires lose grip before the front tires during cornering, causing the car to rotate more than commanded by the steering input. Oversteer requires faster driver reaction than understeer but allows higher cornering speeds in the hands of skilled drivers. Tuned via spring rates, anti-roll bar balance, alignment, and tire choice — most commonly by stiffening the rear or softening the front.
