Final answer:
Hailstones are nearly spherical ice pellets with concentric layers formed by the successive freezing of layers of water.
Step-by-step explanation:
The nearly spherical ice pellets with concentric layers that are formed by the successive freezing of layers of water are called hailstones. Hailstones are commonly observed during thunderstorms and are formed when supercooled water droplets freeze onto nuclei, typically small ice pellets. As these ice pellets are carried upwards by strong updrafts within the storm, they become coated with additional layers of water that freeze, resulting in the formation of concentric layers.