cumulonimbus

American  

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

noun

Meteorology.

plural

cumulonimbus

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 /

plural

cumulonimbi

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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Etymology

Origin of cumulonimbus

First recorded in 1885–90; cumulo- + nimbus

Example Sentences

Lightning is one of the biggest risks, but it is not only the natural lightning from a thunderstorm - or cumulonimbus cloud - that forecasters will be concerned about.

From BBC • Mar. 30, 2026

In these storms, rotations can occur in the base of the cumulonimbus cloud which extends down to the ground.

From BBC • Nov. 7, 2023

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

The woman, with a cumulonimbus frown that grew darker and darker, investigated the commotion.

From "Tristan Strong Punches a Hole in the Sky" by Kwame Mbalia