A snowball is a spherical object made from frozen water or snow, usually created by scooping snow with the hands, and compacting it into a roughly fist-sized ball. The snowball is often used to engage in games, such as snowball fights. The pressure exerted by the hands on the snow is determinant for the final result. Reduced pressure leads to a light and soft snowball. A higher pressure causes the snow to melt, turning into liquid water. Once the pressure is removed, the water turns again into ice, leading to a more compact and hard snowball called an iceball, which eventually can be considered harmful during a snowball fight. The process of melting and refreezing is called regelation.
A snowball may also be a large ball of snow formed by rolling a smaller snowball on a snow-covered surface. The smaller snowball grows by picking up additional snow as it rolls. The terms "snowball effect" and "snowballing" are named after this process. This technique is often used to create snowmen.