cue ball 
noun
The ball, usually a white one, that is to be struck with the cue in snooker, billiards, etc.A player makes a cannon by hitting the object balls with the cue ball....
- The objective is to pocket the object ball using only a center ball hit on the cue ball.
- That is, it seems that the event of the cue ball's striking the nine ball, and the fact that the cue ball struck the nine ball, must have comparable effects.