MARE'S-TAIL

Mare's″–tail′ (?), n. 1. 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. 2. (Bot.) An aquatic plant of the genus Hippuris (H. vulgaris), having narrow leaves in whorls.