cumulonimbus

American  

[kyoo-myuh-loh-nim-buhs] / ˌkyu myə loʊˈnɪm bəs /

noun

Meteorology.

1. a cloud of a class indicative of thunderstorm conditions, characterized by large, dense towers that often reach altitudes of 30,000 feet (9,000 meters) or more, cumuliform except for their tops, which appear fibrous because of the presence of ice crystals: occurs as a single cloud or as a group with merged bases and separate tops.

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cumulonimbus British  

/ ˌkjuːmjʊləʊˈnɪmbəs /

noun

1. meteorol a cumulus cloud of great vertical extent, the top often forming an anvil shape and the bottom being dark coloured, indicating rain or hail: associated with thunderstorms

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cumulonimbus Scientific  

/ kyo̅o̅m′yə-lō-nĭm′bəs /

cumulonimbi plural

1. An extremely dense, vertically developed cloud with a low, dark base and fluffy masses that tower to great heights. Cumulonimbus clouds usually produce heavy rains, thunderstorms, or hailstorms.

2. Also called thundercloud

3. See illustration at cloud

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Other Word Forms

Inflected Forms

noun

• cumulonimbus
  plural

Etymology

Origin of cumulonimbus

First recorded in 1885–90; cumulo- + nimbus

Example Sentences

Heat released within the storm fuels towering cumulonimbus clouds known as "hot towers."

From Science Daily • Jun. 3, 2026

But he adds: "The large cumulonimbus clouds are easy to spot visually unless embedded within other clouds, so we can go around them."

From BBC • Jul. 29, 2025

Warm temperatures allow the atmosphere to hold more humidity, and that humidity is a prerequisite for building clouds—specifically, the tall, menacing cumulonimbus clouds that produce thunder and lightning.

From National Geographic • Sep. 12, 2023

Tornadoes — or rotating funnels of air connected to the Earth and either a cumulonimbus or the base of a cumulus cloud — are dangerous because of their immense power, which Houser barely escaped.

From Salon • Mar. 29, 2023

A large tract of cumulonimbus cloud had rolled in.

From "The London Eye Mystery" by Siobhan Dowd