To defoliate an area or the plants in it means to cause the leaves on the plants to fall off or be destroyed. This is done especially in war to remove protection from an enemy.
例句
Dioxin was the ingredient in Agent Orange, used to defoliate Vietnam.越南戰場上用于毀滅林區的“橙劑”，其成分是二氧雜芑。
英英詞典釋義
Noun
1. the loss of foliage
2. causing the leaves of trees and other plants to fall off (as by the use of chemicals)