cirrus

1 of 2

noun

cir·​rus ˈsir-əs 

plural cirri ˈsir-ˌī 

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

cirr-

2 of 2

combining form

variants or cirri- or cirro- or less commonly cirrhi- or cirrho-

1

: cirrus of a plant or animal

cirriferous

cirrigrade

2

: cirrus cloud

cirrostratus

Examples of cirrus in a Sentence

Recent Examples on the Web

Noun

Noctilucent clouds coalesce from tiny ice water crystals that accumulate in the mesosphere 50 miles (80 kilometres) above Earth's surface — roughly 10 times the height of ordinary cirrus and cloud formations. —Anthony Wood, Space.com, 5 June 2026

Jet fuel combustion produces not just CO₂ but also soot particles that serve as the nuclei for contrail clouds—thin cirrus clouds that capture solar radiation. —Srishti Gupta, Interesting Engineering, 29 Apr. 2026

According to the team, the greatest power losses happen because the dust enhances the presence and reflectance of cirrus clouds, reducing how much radiation that reaches solar panels. —Laura Baisas, Popular Science, 12 Mar. 2026

As the pulse locks in, organ drones arc overhead like streaking cirrus clouds. —Dash Lewis, Pitchfork, 29 Jan. 2026

Word History

Etymology

Noun

New Latin, from Latin, curl

Combining form

Latin cirrus curl

First Known Use

Noun

1708, in the meaning defined at sense 1

Rhymes for cirrus

• cuirass
• pyrus
• papyrus
• veneris

Kids Definition

cirrus

noun

cir·​rus ˈsir-əs 

plural cirri ˈsi(ə)r-ˌī 

: a thin white cloud usually of tiny ice crystals formed at altitudes about 20,000 to 40,000 feet (6,000 to 12,000 meters)

Medical Definition

cirrus

noun

cir·​rus ˈsir-əs 

plural cirri ˈsi(ə)r-ˌī 

: 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