horsetail

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various nonflowering plants of the genus Equisetum, having a jointed hollow stem and narrow, sometimes much reduced leaves.

from The Century Dictionary.

• noun In meteorology, a form of cirrus cloud.
• noun A horse's tail, especially when severed from the body.
• noun A hippurite.
• noun In anatomy, the leash of nerves in which the spinal cord ends: technically called cauda equina. See cauda.
• noun A plant of the genus Equisetum. See cut under Equisetaceæ.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Bot.) A leafless plant, with hollow and rushlike stems. It is of the genus Equisetum, and is allied to the ferns. See Illust. of equisetum.
• noun A Turkish standard, denoting rank.
• noun (Bot.) See Joint-fir.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any of various simple vascular plants, of the family Equisetaceae, that have hollow stems and produce spores.
• noun A Turkish standard denoting rank.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun perennial rushlike flowerless herbs with jointed hollow stems and narrow toothlike leaves that spread by creeping rhizomes; tend to become weedy; common in northern hemisphere; some in Africa and South America