A ball was a spherical projectile launched from a gun. They were made from various materials such as stone, iron, and lead. When fired from a firearm, it served as a bullet. A ball fired from a cannon was also called a cannonball.
In 2364, the bridge crew of the USS Enterprise-D was transported by Q to a planet where they saw soldiers who appeared to be wielding ancient ball-and-powder muskets appropriate to the late-18th century French Army uniforms that they were also wearing. Lieutenant Commander Data claimed that a lead ball propelled by gunpowder would fire one-hundred meters at best with any accuracy. (TNG: "Hide And Q")
In 2373 during the Q Civil War, some Q weapons were perceived as cannonballs and lead charges. (VOY: "The Q and the Grey")