n.forward spin (usually of a moving ball) that is imparted by an upward stroke

Topspin
The topspin backhand drive in tennis: A biomechanical analysis
The tennis topspin forehand drive: Technique changes and critical elements
The aerodynamics of tennis balls—The topspin lob
Kinematics of table tennis topspin forehands: effects of performance level and ball spin
A biomechanical comparison of the topspin and backspin forehand approach shots in tennis
Kinetics of the upper limb during table tennis topspin forehands in advanced and intermediate players.
Trunk and upper limb muscle activation during flat and topspin forehand drives in young tennis players
A biomechanical comparison of the multisegment and single unit topspin forehand drives in tennis
Contributions of upper limb rotations to racket velocity in table tennis backhands against topspin and backspin.