Wikipedia
Riseball
A riseball or dimple is a pitch thrown by a pitcher in fastpitch softball. Upon release by the pitcher, the ball has backspin. The backspin on the ball combined with arm angle and leg lift causes the ball to appear to rise as it moves towards the batter, though in reality it simply falls slower than a similar speed fastball that doesn’t have backspin and therefore has a more level plane on its path to the plate. Jennie Finch is famous for striking out Major League Baseball players with this pitch. The riseball is in effect upside down to a curve ball thrown overhand.
The movement of the ball is caused by the Magnus effect.