A googly is a type of delivery bowlered by a wrist spin bowler. It is occasionally referred to as a Bosie, an eponym in honour of its inventor Bernard Bosanquet.
While a normal leg break spins from the leg to the off side, away from a right-handed batsman, a googly spins the other way, from off to leg, into a right-handed batsman (and is distinct from an off break delivery). The bowler achieves this change of spin by bending the wrist sharply from the normal leg break delivery position. To achieve this bend requires maximal pronation of the forearm prior to delivery, as well as inward rotation of the shoulder: the tip of the elbow, which would normally face the right of a right-hand bowler at the point of delivery, faces upward, and the back of the hand, which would normally face the rear of the bowler, faces the front. When the ball rolls out of the hand (from the side near the little finger, as in a normal leg break), it emerges with clockwise spin (from the bowler's point of view). A googly may also be achieved by bowling the ball as a conventional leg break, but spinning the ball further with the fingers just before it is released.
The change of wrist action can be seen by a skilled batsman and the change of spin allowed for when playing a shot at the ball. Less skilled batsmen, or ones who have lost their concentration, can be deceived completely, expecting the ball to move one direction off the pitch, only for it to move the other direction. If the batsman is expecting a leg break, he will play outside the line of the ball after it spins. This means the ball can either strike the pads for a potential LBW appeal, or may fly between the bat and the pads and hit the wicket.
The googly is a major weapon in the arsenal of a leg spin bowler, and can be one of the bowler's most effective wicket-taking balls. It is used infrequently, because its effectiveness comes mostly from its surprise value.
The grip is identical to that of a conventional leg-break: the only difference is the additional wrist and shoulder rotation, so that the batsman will see the back of the hand when the ball is released.
Read more about this topic: Wrist Spin