Bouncer is a term referred to a delivery, which is pitched very short, in fact banged into the ground with an intention of seeing the ball rise above the shoulder of the batsman. The bouncer is basically an intimidating delivery, the possession of which is a must for a fast bowler.
A weakness in a batsman to negotiate the bouncer is sure to find him in trouble against pacy attacks and on pacy tracks. However, not all bouncers are threatening. Some bouncers that are dug in too short invariably rise too high and thereby harmlessly fly above the batsman's head. But, the ones that rise steeply from a closer range are the ones that have the ability to cause harm if not negotiated properly.
However, the advent of the new Law, which prohibits the bowlers from not bowling more than two bouncers per over in Tests, in a way has robbed the fast bowlers and to an extent some of the charm from Test cricket.
The famed West Indian attack of Geol Garner, Michael holding, Andy Roberts and Malcolm Marshall was renowned for its barrage of bouncers hurled at the batsmen. Bowlers of the calibre of Lillee, Thompson, Imran Khan struck terror in the batsmen with their lethal bouncers.
The protective gear in the form of a helmet was basically invented to protect the batsman form fiery bouncers.