Definition: In table tennis, a backhand is a stroke that is played on the left hand side of the player's body (for a right hander), and vice versa for left handers.
The backhand side of a player is the left hand side of a right hander, and the right hand side for left handers.
The backhand side of the bat (for shakehanders) is the side of the bat used to hit backhand strokes.
