Defoliant

n. chemical substance that removes leaves (from trees, plants, etc.)

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 used for tactical purposes is Agent Orange, which was used widely by the U.S. military during the Vietnam War from 1961 to 1970. Defoliants differ from herbicides in that the former seeks mainly to strip leaves from plants, and the latter is used to destroy or inhibit the growth of plants. Defoliation is not always caused by defoliants. It can be many different environmental factors that cause a plant's leaves to fall off.
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Noun
1. a chemical that is sprayed on plants and causes their leaves to fall off
(hypernym) compound, chemical compound
(derivation) defoliate

v. defoliate

An herbicide that removes leaves from trees and growing plants.