cir·​rus | \ ˈsir-əs How to pronounce cirrus (audio) \
plural cirri\ ˈsir-​ˌī How to pronounce cirrus (audio) \

Definition of cirrus

1 : tendril
2 : a slender usually flexible animal appendage or projection: such as
a : an arm of a barnacle
b : a filament of a crinoid
c : a fused group of cilia functioning like a limb on some protozoans
d : the male copulatory organ of various invertebrate animals
3 : a high wispy white cloud usually of minute ice crystals formed at altitudes between about 20,000 and 40,000 feet (6,000 and 12,000 meters) — see cloud illustration

Examples of cirrus in a Sentence

Recent Examples on the Web One moment the November sky above Cedar Grove Ornithological Research Station was an inert cobalt canvas streaked with a few white cirrus clouds. Paul A. Smith, Milwaukee Journal Sentinel, 4 Dec. 2021 Unfortunately, Rowan-Robinson admitted in a recent research paper that the observations are not high quality and that the region of sky they were captured in is made of filaments of gas known as cirrus. Joshua Hawkins, BGR, 16 Nov. 2021 Carbon emissions are just one part of the industry’s contribution to climate change; nitrogen oxides, which form inside jet engines, and contrail cirrus clouds, which trap heat similar to greenhouse gases, are also major contributors. Dan Catchpole, Fortune, 9 Nov. 2021 Harps, flutes and vibraphones formed dissociating patterns like cirrus clouds atop the thick colors of an organ. Washington Post, 29 Oct. 2021 Since the sun is low to the horizon, those alternating shadows and strips of light were projected onto the underside of the thinner, more diaphanous cirrus clouds, which acted like a canvas for the delicate pastel hues. Washington Post, 5 Oct. 2021 These are clearly very high-altitude cirrus, or ice clouds, definitely not liquid. Washington Post, 16 July 2021 Tom looks at 10 pages of class notes on cumulus, stratus, and cirrus clouds and starts to panic. Brian Platzer, The Atlantic, 23 Mar. 2021 Strong jet stream winds captured some of the system’s upper-level cirrus, or wispy ice clouds at high altitudes, and carried them east across the Blue Ridge and towards the Mid-Atlantic. Washington Post, 15 Jan. 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'cirrus.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of cirrus

1708, in the meaning defined at sense 1

History and Etymology for cirrus

New Latin, from Latin, curl

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Last Updated

18 Dec 2021

Cite this Entry

“Cirrus.” Dictionary, Merriam-Webster, Accessed 16 Jan. 2022.

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More Definitions for cirrus



English Language Learners Definition of cirrus

: a thin type of cloud that forms high in the sky


cir·​rus | \ ˈsir-əs How to pronounce cirrus (audio) \
plural cirri\ ˈsir-​ī \

Kids Definition of cirrus

: a thin white cloud of tiny ice crystals that forms at a very high altitude


cir·​rus | \ ˈsir-əs How to pronounce cirrus (audio) \
plural cirri\ ˈsi(ə)r-​ˌī How to pronounce cirrus (audio) \

Medical Definition of cirrus

: a slender usually flexible animal appendage: as
a : a fused group of cilia functioning like a limb on some protozoans
b : the male copulatory organ of some worms

More from Merriam-Webster on cirrus

Nglish: Translation of cirrus for Spanish Speakers


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