noun
object ball
In cue sports (billiards, pool, snooker), the ball that is the target of a shot, as opposed to the cue ball.
的球をポケットに入れるのが目的です。
The goal is to pocket the object ball.
手球 is the cue ball, the ball struck by the cue, while 的球 is the object ball that is aimed at.
Compound of 的 (target) and 球 (ball).