Sleet is precipitation that falls as small ice pellets after liquid raindrops refreeze before reaching the ground.
In meteorology, the term ice pellets is often used for this form of precipitation. It develops when snow melts while passing through a warm layer of air and then encounters a sufficiently deep layer of freezing air near the surface. The drops freeze into hard or translucent pellets before landing.
Sleet differs from freezing rain, which remains liquid until it strikes a cold surface and then freezes into a glaze. It also differs from hail, which grows inside strong thunderstorm updrafts and is usually larger. Graupel consists of soft, rimed snow pellets rather than hard refrozen raindrops.
The exact everyday meaning of “sleet” varies by region. In the United States it commonly means ice pellets, while in parts of the United Kingdom the word may refer to a mixture of rain and snow.