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late 15c., past participle adjective from Middle English verb disesen "to make uneasy; inflict pain" (mid-14c.), later "to have an illness or infection" (late 14c.); "to infect with a disease" (late 15c.), from disease (n.).
diseased dis·eased (dĭ-zēzd')
Affected with disease.
Unsound or disordered.