cumulonimbus

American  

[kyoo-myuh-loh-nim-buhs] / ˌkju mjə loʊˈnɪm bəs /

noun

Meteorology.

• cumulonimbus
  plural

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

Noun Inflected Forms

• cumulonimbus
  plural

Etymology

Origin of cumulonimbus

First recorded in 1885–90; cumulo- + nimbus

Example Sentences

See Examples For:

cumulonimbus

Hail is most common in summer months as it needs to develop inside towering cumulonimbus clouds, which are often spawned by intense heat at ground level.

From BBC ● Aug. 3, 2026

Then, when the surrounding air has become heated enough, it forms a column with an anvil-shaped cloud -- the cumulonimbus.

From Barron's ● Jul. 27, 2026

Also called a cumulonimbus flammagenitus, they can occur during volcanic eruptions or, as in this case, when a wildfire roasts the air near the ground, causing it to rise quickly.

From Barron's ● Jul. 27, 2026

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

From Science Daily ● Jun. 3, 2026

Hail is a shower of irregular lumps of ice and always comes from cumulonimbus clouds, so I knew 1 was right under the cloud I’d seen forming earlier.

From "The London Eye Mystery" by Siobhan Dowd