a wisp of trailing cirrus cloud, often indicating high winds in the upper troposphere
2.
an erect cosmopolitan pond plant, Hippuris vulgaris, with minute flowers and crowded whorls of narrow leaves: family Hippuridaceae
mare's-tail in American English
(ˈmɛrzˌteɪl)
noun
1.
long, narrow formations of cirrus cloud somewhat like a horse's tail in shape, supposed to be a sign of changes in the wind
2.
the only species (Hippuris vulgaris) of an aquatic family (Hippuridaceae, order Callitrichales) of plants with tiny flowers and narrow, hairlike leaves growing in thick whorls around the slender, erect stems