Slush, also called slush ice, is a slurry mixture of small ice crystals (e.g. snow) and liquid water.

In the natural environment, slush forms when ice or snow melts or during mixed precipitation. This often mixes with dirt and other pollutants on the surface, resulting in a gray or muddy brown color. Often, solid ice or snow can block the drainage of fluid water from slushy areas, so slush often goes through multiple freeze/thaw cycles before being able to completely drain and disappear.

In areas where road salt is used to clear roadways, slush forms at lower temperatures in salted areas than it would ordinarily. This can produce a number of different consistencies over the same geographical area with scattered salted areas covered with slush and others covered with frozen precipitation .