Used attributively to describe something fast or forceful, e.g., "a cannonball train".
Definitions
Moving very fast or with great force, like a cannonball. A cannonball sprint down the court left the defenders stunned.
Exclamation shouted before making a cannonball jump.
Definitions
An exclamation shouted before performing a cannonball jump into water or to announce such an action. "Cannonball!" he shouted before plunging into the lake.