The definition of a ball is a round object that is used for a variety of activities, such as sports, games, and recreation. Balls are typically made of rubber, plastic, leather, or cloth, and come in a variety of sizes and colors. The most common type of ball is a soccer ball, but there are many other types of balls, such as basketballs, baseballs, tennis balls, and volleyballs. Balls can also be used for a variety of purposes, such as for throwing, bouncing, and rolling. Additionally, some balls have a valve, which is a small opening that allows air to escape when the ball is compressed. Valves are used to regulate the pressure inside the ball, which can affect its performance and durability. Balls are an essential part of many activities, and they come in a variety of shapes, sizes, and materials.