Definition

1. Noun:
   • A type of dense, towering cloud: A cumulonimbus is a specific type of cloud characterized by its great vertical height, dark appearance, and association with thunderstorms, heavy rain, hail, lightning, and sometimes tornadoes. It is often described as having a flat, anvil-shaped top.

Examples of Usage

• Noun:
  • The sky turned dark as a massive cumulonimbus approached from the west.
  • Meteorologists warned that the cumulonimbus clouds could produce severe weather.
  • The anvil top of the cumulonimbus was visible for miles.

Advanced Usage

• "Cumulonimbus incus": The technical term for a mature cumulonimbus cloud that has developed the characteristic anvil shape (incus means 'anvil' in Latin).
  • The storm system was dominated by a well-developed cumulonimbus incus.
• "Cumulonimbus calvus": A stage in the development of a cumulonimbus cloud where it is towering but the top has not yet formed into a distinct anvil.
  • The cumulonimbus calvus indicated the thunderstorm was still intensifying.

Variants and Related Words

• Cumulus (noun): A genus of clouds to which cumulonimbus belongs; they are puffy, fair-weather clouds that can develop into cumulonimbus.
  • The small, white cumulus clouds grew into threatening storm clouds by afternoon.
• Nimbostratus (noun): Another type of rain cloud, but it is a thick, dark, layered cloud that brings steady precipitation, unlike the turbulent, vertical cumulonimbus.
  • The forecast calls for drizzle from nimbostratus clouds, not thunderstorms from cumulonimbus.

Synonyms

• Thunderhead: An informal term for the upper portion of a cumulonimbus cloud.
• Storm cloud: A general term for clouds associated with storms, which often refers to cumulonimbus.

Related Phrases

• Cumulonimbus cloud: The full, most common phrase used to describe this cloud type.
  • The formation of cumulonimbus clouds is a key indicator of potential severe weather.
• Cumulonimbus mammatus: A pattern of pouch-like clouds sometimes hanging from the anvil of a cumulonimbus, often associated with severe thunderstorms.
  • The eerie beauty of cumulonimbus mammatus appeared after the worst of the storm had passed.

Related Idioms

• "On the horizon": While not exclusive to clouds, this idiom is often used when describing the approach of a cumulonimbus cloud as a metaphor for impending trouble or a significant event.
  • A conflict was on the horizon, as unmistakable as a gathering cumulonimbus.

Noun

1. a dark cloud of great vertical extent charged with electricity; associated with thunderstorms