can·non·ball also cannon ball 
(kănən-bôl′)
(kănən-bôl′)n.
1. A round projectile fired from a cannon.
2. A jump into water made with the arms grasping the upraised knees, usually intended to make a big splash.
3. Something, such as a fast train, that moves with great speed.
4. Sports A fast low serve in tennis.
intr.v. can·non·balled, can·non·ball·ing, can·non·balls
1. To travel with great speed.
2. To jump into water while grasping one's upraised knees with one's arms.