cumulus
Americannoun
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cumulus
plural
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a heap; pile.
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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.
noun
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cumuli
plural
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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.
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See illustration at cloud
Other Word Forms
Noun Inflected Forms
Etymology
Origin of cumulus
1650–60; < New Latin ( Latin: mass, pile)
Vocabulary lists containing cumulus
Weather and Climate - Introductory
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Weather and Climate - Middle School
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Earth Science - Middle School
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The results can be seen in images such as this: a luminous, tonally rich seascape of cumulus clouds drifting over the Bay of Naples.
From The Wall Street Journal ● Sep. 23, 2026
It starts off as a cute little white cloud -- a cumulus cloud, which is formed because water vapour has turned into tiny droplets.
From Barron's ● Jul. 27, 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
A recent study found that cumulus clouds, the small cotton ball-like ones typical for a sunny day, can dissipate once an eclipse begins.
From New York Times ● Apr. 8, 2024
Monday morning was blue and white, and everything was blowing: cumulus clouds, bare branches, scraps of rubbish.
From "Chasing Vermeer" by Blue Balliett
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
