1) Chemical compound 2) Chemical sprayed on plants 3) Compound 4) Crop disease 
A defoliant is any chemical sprayed or dusted on plants to cause its leaves to fall off. A classic example of a highly toxic defoliant is Agent Orange, which the British military used abundantly to defoliate regions of Malaya during the Malayan Emergency, and the U.S. military to defoliate regions of Vietnam during the Vietnam War from 1961 to 197...
Substance used for removal of leaves by its toxic action on living plants.
a chemical dust or spray applied to plants to cause their leaves to drop off prematurely. Defoliants sometimes are applied to crop plants such as ...
A chemical that removes leaves from trees and growing plants
Any substance or mixture of substances when applied to a plant causes the leaves or foliage to drop, with or without causing abscission.
A chemical that causes leaves to wither and die on plants.
It is a chemical sprayed on plants that causes leaves to fall of prematurely.
[n] - a chemical that is sprayed on plants and causes their leaves to fall off
An herbicide that removes leaves from trees and growing plants. 
noun a chemical that is sprayed on plants and causes their leaves to fall off
a preparation for defoliating plants.