Slower one is a term referred to a delivery that is bowled at a much slower pace than the one bowled at the regular pace. It is a delivery that is normally found in the repertoire of a fast bowler. It is bowled so as to fox the batsman into playing early and thereby ending up spooning the ball in the air.
In the execution of the slower one the arm action is maintained at the same speed while it is only the ball that travels at a slower pace. The execution of the slower one varies from bowler to bowler. Some bowlers grip the ball closer so as to touch the palm, while some let it from the back of the hand. Some employ the off spin action to add some turn to the ball.
These days the slower one is used regularly during the slog overs of a One-day game. Venkatesh Prasad of India is a master of the slower-one and puts it to good effect during the One-dayers.