Bottoming out is when a formula 1 car’s underbody hits the track surface. To get a low center of gravity and to create downforce, F1 cars already have a very low ride height. Ride Height is the distance between the bottom of the car and the road.
When going through a corner or at high speed, with sharp compression of the suspension, the ride height becomes even lower. The underbody of F1 cars contains a wooden plank to measure ride height. So in case of bottoming out, the car leaves a brown trail on the track.
Bottoming out is more likely to happen when there are sudden bumps or kerbs on the track.