Definition of acquired immunodeficiency syndrome

acquired immunodeficiency syndrome (uh-KWY-erd IH-myoo-noh-deh-FIH-shun-see SIN-drome): A disease caused by the human immunodeficiency virus (HIV). People with acquired immunodeficiency syndrome are at an increased risk for developing certain cancers and for infections that usually occur only in individuals with a weak immune system. Also called AIDS.