premise: A man in a motocross race has just turned over his motorcycle as two other riders prepare to overtake him. hypothesis: A man in a motocross race overturns his motorcycle just as two other fellow competators pass him on the track outside.
entailment: If the riders are preparing to overtake him, they are in the race as well, and are therefore competitors. Overturns is a rephrasing of turned over. If they prepare to overtake him, it follows that they pass him.