1. plural of cumulonimbus; large, towering clouds that produce thunderstorms, heavy rain, and severe weather
Usage: meteorology; plural form

Examples

• The meteorologist warned that massive cumulonimbi were forming on the horizon.
• Pilots avoid flying through cumulonimbi due to dangerous turbulence and lightning.
• The afternoon heat caused several cumulonimbi to develop rapidly.
• Cumulonimbi can reach heights of over 40,000 feet.
• The storm system contained multiple cumulonimbi stretching across three states.
• Weather radar clearly showed the cumulonimbi approaching the city.