1.The separation of ripened leaves from a branch or stem; the falling or shedding of the leaves.
2.The act or process of causing plants to lose their leaves, especially by application of a chemical agent. Note: The deliberate defoliation of plants has been used in war (as in Vietnam) to deprive an enemy of cover and allow attack from the air; also, to destroy narcotic-producing plants as a tactic against illegal drug production. The chemical defoliating agents are often sprayed over large areas from airplanes.