Dictionary:

equisetum

  (ĕk'wə-sē'təm)

See horsetail.

[Latin equisaetum, horsetail : equus, horse + saeta, bristle, stiff hair.]

Genus of the fern ally family Equisetaceae. These plants have a high content of thiaminase, and horses which eat a lot of them, usually in their hay, develop thiamin deficiency. This is characterized by incoordination, falling, bradycardia and severe cardiac irregularity. Response to treatment with thiamin is rapid and complete.
Includes E. arvense, E. hyemale, E. laevigatum, E. limosum, E. palustre, E. ramosissimum. Called also horsetails, foxtails, marestails.

The botanical name for horsetail and scouring rush.

The noun has one meaning:

Meaning #1: horsetails; coextensive with the family Equisetaceae
  Synonym: genus Equisetum