any tracheophyte plant of the genus Equisetum, having jointed stems with whorls of small dark toothlike leaves and producing spores within conelike structures at the tips of the stems: phylum Sphenophyta
2.
a stylized horse's tail formerly used as the emblem of a pasha, the number of tails increasing with rank
horsetail in American English
(ˈhɔrsˌteɪl)
noun
1.
a horse's tail
2.
any of the only surviving genus (Equisetum) of a division (Equisetophyta) of plants having hollow, jointed stems, with scalelike leaves at the joints and spores borne in terminal cones; scouring rush