mare's-tail

[ mairz-teyl ]
/ ˈmɛərzˌteɪl /

noun

a long narrow cirrus cloud whose flowing appearance somewhat resembles a horse's tail.
an erect, aquatic, Old World plant, Hippuris vulgaris, having crowded whorls of narrow, hairlike leaves.

Origin of mare's-tail

First recorded in 1755–65

British Dictionary definitions for mare's-tail

mare's-tail

noun

a wisp of trailing cirrus cloud, often indicating high winds in the upper troposphere
an erect cosmopolitan pond plant, Hippuris vulgaris, with minute flowers and crowded whorls of narrow leaves: family Hippuridaceae