Note: It is unclear whether the type of cloud (stratified) and the word “pellet” may still be being added to the question in some authorities. Austro Control do not include these, according to recent feedback.

ICE PELLETS (PL). Ice particles, transparent/translucent pellets, spherical or irregular. 
Diameter of 5 mm or less. 
Fall from layered cloud. 
They often bounce when they hit the ground.

• Ice pellets form when snowflakes start to melt as they fall from the cloud, then fall through sub-freezing air where they re-freeze into grain-like particles.

If Ice Pellets are observed on the ground it means that at higher altitude these ice pellets were not solid, but they existed in the form of super-cooled water droplets (freezing precipitation). It could also be that these pellets were snowflakes that melted in a warmer air region then re-froze, as can happen around warm fronts.