Mare's"-tail` (?), n.
1.
A long streaky cloud, spreading out like a horse's tail, and believed to indicate rain; a cirrus cloud. See Cloud.
Mackerel sky and mare's-tails
Make tall ships carry low sails.
Old Rhyme.
2. Bot.
An aquatic plant of the genus Hippuris (H.vulgaris), having narrow leaves in whorls.
© Webster 1913.