mare's tail

noun

plural mare's tails or mares' tails

1

a

: a common aquatic plant (Hippuris vulgaris of the family Plantaginaceae, the plantain family) with elongated shoots having dense whorls of narrow finely tapered leaves

b

: horseweed sense 1

2

: a cirrus cloud that has a long slender flowing appearance

Word History

First Known Use

15th century, in the meaning defined at sense 1a