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[kyoo-myuh-luh s] /ˈkyu myə ləs/
noun, plural cumulus.
a heap; pile.
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.
Origin of cumulus
1650-60; < New Latin (Latin: mass, pile) Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for cumulus
Contemporary Examples
Historical Examples
  • The moon was now well up, but hidden by a mass of cumulus cloud.

  • I have, however, failed to meet with any trace of the cumulus in my sections.

  • As the cumulus belongs to the day, so does the Stratus to the night.

    The Rain Cloud Anonymous
  • There were cumulus clouds of varying closeness all the time.

    Farthest North Fridtjof Nansen
  • It is of interest to note the appearance of the sky when cumulus clouds are present.

    Visual Illusions Matthew Luckiesh
  • cumulus clouds on sunny days are generally at altitudes of 4000 to 7000 feet.

    Visual Illusions Matthew Luckiesh
  • cumulus clouds, when they are well defined, and advance with the wind, foretell fine weather.

    The Reason Why Anonymous
  • The cumulus is another form of cloud, which floats along in fleecy masses, in the days of summer, but dissolves at night.

British Dictionary definitions for cumulus


noun (pl) -li (-ˌlaɪ)
a bulbous or billowing white or dark grey cloud associated with rising air currents Compare cirrus (sense 1), stratus
(histology) the mass of cells surrounding a recently ovulated egg cell in a Graafian follicle
Word Origin
C17: from Latin: mass
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for cumulus

1650s, "a heap," from Latin cumulus "a heap, pile, mass, surplus," from PIE *ku-m-olo-, suffixed shortened form of root *keue- "to swell" (cf. Sanskrit svayati "swells up, is strong," Greek kyein "to swell," Lithuanian šaunas "firm, solid, fit, capable"). Meteorological use for "rounded mass of clouds" first attested 1803.

Online Etymology Dictionary, © 2010 Douglas Harper
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cumulus in Science
Plural cumuli (kym'yə-lī')
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. See illustration at cloud.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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