A Rock bouncer is a four wheel drive buggy with a high horsepower engine that drives up a slope that you can't hardly walk up without a rope and they have enough horsepower that the whole buggy bounces up and down as the tires get traction and lose traction.
Often, they will load water into at least the front tires if not all four tires to get the center of gravity down lower so that they are less likely to flip over backwards and go tumbling down the hill. They will also generally run what they call stickies which are a tire with a very soft compound so that it kind of sticks to the rock. They will usually have over built drive trains to handle the shock loads when the tires get traction otherwise they would shred their axles, driveshafts, transfer cases, etc.
Aaron Z