What does cirri mean?
Cirri is the plural of cirrus, a term with two principal uses. In meteorology, cirri are the highest of the main cloud types: thin, white, wispy clouds of ice crystals drifting at altitudes above roughly six kilometres, often forming delicate streaks or tufts across an otherwise blue sky. Because they appear ahead of approaching weather systems, their presence can signal that rain or a front may arrive within a day or so. In biology, cirri refers to small, slender, curling appendages found on certain animals — for example, feeding structures on barnacles or tentacle-like filaments on sea anemones — and occasionally to hair-like parts of plants. The word comes directly from Latin, where cirrus meant a curl or lock of hair, a fitting image for both the feathered clouds and the fine tendrils of living things. It belongs chiefly to scientific and formal writing rather than casual conversation.
nounCirri is the plural of cirrus, referring to thin, wispy white clouds composed of ice crystals found at high altitudes, or to slender curling appendages such as the tentacle-like structures on certain marine animals.
- Plural of cirrus: thin, wispy, white clouds made of ice crystals at high altitudes.
- Plural of cirrus in zoology and botany: slender, curling appendages or filaments, such as the tentacles of sea anemones or similar structures on plants.
"High overhead, delicate cirri streaked the winter sky like brushstrokes of white silk."
"By dawn, the cirri had thickened into a milky veil that softened the morning sun."
"Under the microscope, the anemone's cirri waved gently in the current."
Cirri is itself the standard plural of cirrus, following the Latin second-declension pattern (-us → -i). It has no further plural.
"A single cirrus drifted past, but soon the whole sky was streaked with cirri."
Those feathery clouds painted across the sky have been called 'cirri' since Latin speakers used the same word for a curling lock of hair — the sky's own flowing tresses.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cirri
Cirri derives from the Latin noun cirrus, meaning a curl, ringlet, or lock of hair. The meteorological sense was established in the early 19th century when Luke Howard's cloud classification system adopted the Latin word for the wispy, hair-like high clouds. The same root underlies the related cloud names cirrostratus and cirrocumulus and the adjective cirriform, all built from the identical Latin stem.
Related word forms
How cirri is actually used
Formal to technical register; most common in meteorology, where it appears alongside related cloud terms, and in scientific descriptions of marine life. In everyday speech, people more often say 'cirrus clouds' than 'cirri'.
Easily confused with cirri
Cirrus is the singular form denoting one wisp or a single cloud type, while cirri is its plural, used when referring to several such clouds or appendages.