crazyweed

from The Century Dictionary.

• noun A name given to various plants growing in the western United States, the eating of which by horses and cattle producesemaciation, nervous derangements, and death: often called loco-weed (which see). Among them are species of Astragalus, Oxytropis, and perhaps some plants of other genera.

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

• noun any of several leguminous plants of Western North America causing locoism in livestock.

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

• noun any of several leguminous plants of western North America causing locoism in livestock
• noun any of several leguminous plants of western North America causing locoism in livestock