defoliant[dē fō′lē ənt]
defoliant definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a chemical substance that causes leaves to fall from growing plants
defoliant definition by American Heritage Dictionary
A chemical sprayed or dusted on plants to cause the leaves to fall off.