snowball

A snowball is a lump of snow formed by pressing snow together or by rolling a mass along the ground so that it sticks.

The ability to form a cohesive snowball depends on the snow's moisture content. Wet, packing snow with some cohesion packs easily, while dry, powdery snow resists compression. The size of a snowball grows as more snow is added, and larger balls can be created by rolling multiple layers together or by stacking successive packs.

In recreational contexts, snowballs are most commonly used in snowball fights and winter games. While soft, well-packed snowballs are generally safe, hard-packed or icy cores can cause injury if thrown with force. People often wear gloves to protect hands and reduce melting during play.

The term snowball also appears in metaphorical uses, such as the snowball effect, whereby small actions build over time into a large outcome. In social science, snowball sampling refers to a recruitment method in which existing participants refer other participants.

Snowballs melt as air temperature rises, and they are a common feature of winter landscapes where snow persists on the ground.