Backspin

Backspin is a type of rotational spin on a ball in which the ball spins opposite to its direction of travel. It is typically produced by brushing the ball from underneath or behind with the striking implement, imparting retrograde rotation around a roughly horizontal axis.

In flight, backspin interacts with air through the Magnus effect to influence lift and stability. It generally slows forward motion, can alter the trajectory, and, upon landing, reduces rebound height and can cause the ball to skid or bite the surface depending on surface speed and spin amount.

In table tennis, backspin (often called underspin) is common on defensive returns and chops; it can cause opponents to misread the rebound and prefer aggressive topspin. In tennis, the slice backhand or approach shot uses backspin to keep the ball low and reduce bounce, aiding control and gap creation.

In golf, backspin is produced by a descending strike with lofted clubs and influences carry, descent angle, and stopping power on greens; higher backspin can help the ball stop quickly after landing. In billiards or pool, backspin on the cue ball is used to draw the ball backward after impact, affecting position play.

Spin rate is usually measured in revolutions per minute (RPM) or radians per second, and modern equipment and training tools quantify spin to aid technique, equipment selection, and performance analysis.