1. Any of various gymnospermous, mostly shrubby plants of the genus Ephedra, some of which are used as a source of ephedrine.
2. A stimulant, often sold as pills or tablets, derived from a plant of this genus.

[Latin ephedra, horsetail, from Greek ephedrā, from feminine of ephedros, sitting upon : ep-, epi-, epi- + hedrā, seat.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.