cumulus

American  

[kyoo-myuh-luhs] / ˈkyu myə ləs /

noun

plural

cumulus

1. a heap; pile.

2. a cloud of a class characterized by dense individual elements in the form of puffs, mounds, or towers, with flat bases and tops that often resemble cauliflower: as such clouds develop vertically, they form cumulonimbus.

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cumulus British  

/ ˈkjuːmjʊləs /

noun

1. a bulbous or billowing white or dark grey cloud associated with rising air currents Compare cirrus stratus

2. histology the mass of cells surrounding a recently ovulated egg cell in a Graafian follicle

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cumulus Scientific  

/ kyo̅o̅m′yə-ləs /

plural

cumuli

1. A dense, white, fluffy cloud with a flat base, a multiple rounded top, and a well-defined outline. The bases of cumulus clouds form primarily in altitudes below 2,000 m (6,560 ft), but their tops can reach much higher. Cumulus clouds are generally associated with fair weather but can also bring rain when they expand to higher levels. The clouds' edges are well-defined when they are composed of water droplets and fuzzy when made up of ice crystals.

2. See illustration at cloud

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Etymology

Origin of cumulus

1650–60; < New Latin ( Latin: mass, pile)

Example Sentences

"We'll have to monitor those feisty cumulus clouds and potentially a few showers and breezes as well," Mark Burger, the launch weather officer, said Tuesday.

From Barron's • Apr. 1, 2026

The weather rules include atmospheric electricity, types of cloud, specifically cumulus and disturbed weather like rain or strong winds.

From BBC • Mar. 30, 2026

Meanwhile, in Virginia, several old text messages swallowed attorney general nominee Jay Jones in a cumulus of controversy.

From Los Angeles Times • Nov. 30, 2025

As that sinister cumulus rose above an oval-shaped reservoir, it collapsed, sending red-hot embers down the steep slopes toward Greenville in a storm of torched trees and exploding shrubs.

From Salon • Jun. 6, 2023

It was as the inheritor of a view which covered a dozen miles of rollers, and hundreds of miW of cumulus.

From "The Once and Future King" by T. H. White