What does ibw mean in cricket?

Answer 1

Leg Before Wicket.

It's where the leg is in between the ball and the wicket and the ball hits the leg. It is classified as if the ball had actually hit the wicket.

See related link for more information.

Answer 2

Leg before wicket-when your leg covers the wicket when the ball hat hit the leg. Only taken into concideration when the batsman is not playing a shot and when the ball has pitched in line with the wickets.