course of a thrown ball; ball trajectory
Used mainly in baseball for the path of a pitched or thrown ball.
彼の投げる球筋はとても鋭い。
The trajectory of his pitches is very sharp.
course of a hit ball; ball flight
Used in golf, tennis, and similar sports for the path of a struck ball.
ゴルフでは風が球筋に大きく影響する。
In golf, the wind greatly affects the ball's flight.