the type of dense cloud that develops vertically through all cloud levels, consisting of water droplets, ice crystals, and sometimes hail, and associated with thunder, lightning, and heavy showers
nounpl. cu·mu·lo·nim·bus·es or cu·mu·lo·nim·bi
An extremely dense, vertically developed cumulus with a low dark base and fluffy masses that extend to great heights, usually producing heavy rains, thunderstorms, or hailstorms.
- A cloud, with a tall structure and a flat base, that is often associated with thunderstorms.