- 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
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- 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