What is a bumper in bowling

I do not play bowling in my life till now. What is bumper in bowling, I have no idea.

I see that Owl gave you a detailed and satisfactory reply. I do not play bowling.

It depends, I believe, on what kind of bowling you are talking about. In ten-pin bowling, 'bumper bowling' is when the gutters are covered and the ball can bounce off the sides without going into the gutter. In lawn bowls, if the term exists - and I can't find any reference to it - I would have said that a 'bumper' was either when your bowl hits another one, knocking it out of the way (or closer to the jack, if you aren't so lucky), or maybe when the bowl is delivered so that it bounces rather than rolls (which would be bad practice, I think, in that sport, if not illegal!) In Cricket, a 'bumper' is another term for a 'bouncer' as often bowled by a fast bowler, the object being to delver the ball (after bouncing) at chest height so that the batsman has to move his weight to his back foot and raise the bat to chest height to avoid being hit.