- long, narrow formations of cirrus cloud somewhat like a horse's tail in shape, supposed to be a sign of changes in the wind
- 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 slender, erect stems
- horseweed (sense )
nounpl. mare's-tails, or mares'-tails
- A cosmopolitan aquatic herb (Hippuris vulgaris) having inconspicuous flowers and linear whorled leaves on erect unbranched stems.
- See horseweed.
- A long narrow cirrus cloud with a flowing appearance.
(plural mare's-tails or mares'-tails)
- A long streaky cloud, spreading out like a horse's tail, and believed to indicate rain; a cirrus cloud.
- An aquatic plant, Hippuris vulgaris, having narrow leaves in whorls.
Part or all of this entry has been imported from the 1913 edition of Webster's Dictionary, which is now free of copyright and hence in the public domain. The imported definitions may be significantly out of date, and any more recent senses may be completely missing.