cannonball
/ˈkænənbɔːl/noun
1- a round metal or stone projectile fired from a cannon in former times（旧时大炮发射的金属或石制的圆形）炮弹。
1.1
- （亦作cannonball dive）N. Amer. a jump into water feet first with the knees clasped to the chest〈北美〉抱膝跳水。