What does cirrus mean?
Cirrus refers to the highest family of common clouds — thin, white, feathery sheets or filaments that form above about 6,000 meters (20,000 feet), where temperatures are cold enough for water vapor to freeze into ice crystals. The name comes from the Latin word for a curl or lock of hair, chosen because these clouds resemble delicate wisps or tufts drifting across the sky. In everyday usage, cirrus is chiefly encountered in weather reports and forecasts, where spreading veils of cirrus are a classic early sign that a warm front — and often rain within a day or so — is on the way. The term also appears in biology, where it describes slender, hairlike or curling structures such as the tendrils of climbing plants or the small appendages of certain aquatic animals. Because it is a precise scientific label rather than a casual word, cirrus carries an air of technical authority while remaining vividly descriptive.
A high-altitude cloud of ice crystals forming thin, white, wispy or feathery patches, typically above 20,000 feet (about 6,000 meters).
"Streaks of cirrus caught the last light of sunset."
Often used collectively; the plural 'cirri' is reserved mainly for scientific writing.
In zoology and botany, a slender, curling filament or appendage, such as a tendril or a hairlike structure on an animal.
"The barnacle extends its cirri to filter food particles from the water."
Almost exclusively used in technical scientific contexts.
The plural 'cirri' is the standard Latinate plural, used mainly in scientific and technical writing for both cloud and anatomical senses. In casual meteorological discussion, 'cirrus' is frequently treated as a mass noun.
"The microscope revealed rows of fine cirri along the organism's edge."
The word 'cirrus' literally means a 'lock of hair' in Latin — meteorologists named the cloud after its resemblance to a flowing wisp of curls.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cirrus
Cirrus comes directly from Latin, where the noun meant a curl, fringe, or lock of hair. English adopted it in the late 18th century, when Luke Howard's influential cloud classification system (1803) assigned the Latin name to the high, wispy cloud type we still call cirrus today. The same root underlies the related cloud names cirrocumulus and cirrostratus, as well as the adjectives cirrate and cirrose used for hairlike or fringed structures in zoology and botany.
Related word forms
How cirrus is actually used
Primarily a technical term used in meteorology, aviation, and biology rather than everyday conversation. In weather forecasting, extensive cirrus often signals an approaching frontal system. The plural 'cirri' is standard in scientific contexts for both the cloud sense and the anatomical/botanical sense.
Easily confused with cirrus
A cirque is a bowl-shaped hollow carved by a glacier in mountainside terrain, whereas cirrus is a type of high, wispy cloud.