an animal or plant that lives on or in another animal or plant of a different type and feeds from it

The older drugs didn't deal effectively with the malaria parasite. 以前的药物不能有效对付引起疟疾的寄生虫。

a person who is lazy and lives by other people working, giving them money, etc.

Financial speculators are parasites on the national economy. 金融投机者是国民经济的寄生虫。