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[kyoo-myuh-loh-nim-buh s] /ˌkyu myə loʊˈnɪm bəs/
noun, plural cumulonimbus.
a cloud of a class indicative of thunderstorm conditions, characterized by large, dense towers that often reach altitudes of 30,000 feet (9000 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.
Also called thundercloud, thunderclouds, thunderhead.
Origin of cumulonimbus
1885-90; cumulo- + nimbus


or thunderclouds

[thuhn-der-kloud] /ˈθʌn dərˌklaʊd/
1690-1700; thunder + cloud Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the Web for thunder-clouds
Historical Examples
  • The huge waves rose black as thunder-clouds, hurled their white froth toward heaven, and sank with sullen roar back into the deep.

    Fairy Circles Unknown
  • "These are thunder-clouds driving under us," replied her mother.

    The Sand-Hills of Jutland Hans Christian Andersen
  • It was swept by the close-range fire of the Germans, like rain from thunder-clouds.

    The Irish at the Front Michael MacDonagh
  • So he sent them above, where they became the thunder-clouds.

  • She seemed molded from fire and air, and vivified at some Voltaic pile of August thunder-clouds heaped against the sunset.

    Pierre; or The Ambiguities Herman Melville
  • Her blue eyes were dark as thunder-clouds in their earnestness.

    The Hunted Woman James Oliver Curwood
  • The sea in the offing was black and rolling; thunder-clouds lay low on the horizon, split by broad flashes of lightning.

    The Law and the Lady Wilkie Collins
  • The height of these thunder-clouds has been much under-estimated.

  • A hot July, winged with thunder-clouds, brooded over the meadows by the Whit.

    A Charming Fellow, Volume II (of 3) Frances Eleanor Trollope
  • It had piled the thunder-clouds high and higher, and now and again a heavy drop of rain tapped at her window like a thrown pebble.

    Riders of the Silences John Frederick
British Dictionary definitions for thunder-clouds


noun (pl) -bi (-baɪ), -buses
(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


a towering electrically charged cumulonimbus cloud associated with thunderstorms
anything that is threatening
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 thunder-clouds



1887, from cumulo-, comb. form of cumulus, + nimbus.

Online Etymology Dictionary, © 2010 Douglas Harper
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thunder-clouds in Science
Plural cumulonimbi (kym'yə-lō-nĭm'bī)
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. Also called thundercloud. See illustration at cloud.
See cumulonimbus.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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