equisetum

from WordNet (r) 3.0 (2006)

Equisetum
    n 1: horsetails; coextensive with the family Equisetaceae [syn:
         {Equisetum}, {genus Equisetum}]

from The Collaborative International Dictionary of English v.0.48

Equisetum \Eq`ui*se"tum\, n.; pl. {Equiseta}. [L., the
   horsetail, fr. equus horse + seta a thick,, stiff hair,
   bristle.] (Bot.)
   A genus of vascular, cryptogamic, herbaceous plants; -- also
   called {horsetails}.
   [1913 Webster]

   Note: The {Equiseta} have hollow jointed stems and no true
         leaves. The cuticle often contains siliceous granules,
         so that one species ({E. hyemale}) is used for scouring
         and polishing, under the name of {Dutch rush} or
         {scouring rush}.
         [1913 Webster]