What does it mean if the suspension bottom out?

If a car "bottoms out" it means that it has been in a situation where the underside of the car hits the road. If this condition continues, there will be severe damage to the vehicle suspension and if definitely a SEVERE safety hazard. Things that can cause a vehicle to "bottom out" are , poor driving habits (not slowing down for road hazards like speed bumps, holes in roads, etc) or bad suspension parets like struts, shocks, upper or lower control arms, bad sway bar bushing and end links.

If it only happened once, then it can probably be caused by road conditions but5 it is a symptom of something wrong. Get the car checked. For your own safety.