A cirrus cloud formation resembling horse tails.

plural of mare's-tail

A long streaky cloud, spreading out like a horse's tail, and believed to indicate rain; a cirrus cloud. / Any aquatic plant of the genus Hippuris, having narrow leaves in whorls.

plural of mare's-tail

plural of mare's tail

Any of the water plants in the genus Hippuris, / Conyza canadensis, an annual weed also known as horseweed and Canadian fleabane; / Equisetum spp., fern allies also known as horsetail and pipeweed.

Cirrus clouds forebode bad weather.

Alternative form of mackerel sky and mare's-tails make tall ships carry low sails