mare's-tail
noun1
A long streaky cloud, spreading out like a horse's tail, and believed to indicate rain; a cirrus cloud.
2
Any aquatic plant of the genus Hippuris, having narrow leaves in whorls.
3
especially, common mare's tail (Hippuris vulgaris)
4
Erigeron canadensis (syn. Conyza canadensis), an annual weed.
5
Equisetum, a fern ally.