• synonyms


  1. a combining form representing cumulus in compound words.
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Also cumuli-; especially before a vowel, cumul-.

Origin of cumulo-

see origin at cumulus, -o-
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for cumuli

Historical Examples

  • There must be text-books on how to tell the cumuli from the cirrus.


    Simeon Strunsky

  • Some are close-packed and dense, like cumuli; some are wispy or mottled, like cirri.

    Curiosities of the Sky

    Garrett Serviss

  • At sunset the thermometer was at 55°; the evening clear and calm, with some cumuli.

  • The moon emerged from behind a cloud, touching with a delicate sepia some fleecy edge of cumuli.

    The Record of Nicholas Freydon

    A. J. (Alec John) Dawson

  • White clouds rising in the east gather into cumuli, with an increasing blackness along their lower portions.

    The Desert World

    Arthur Mangin

cumuli in Science


Plural cumuli (kyōōmyə-lī′)
  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. See illustration at cloud.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.