<p><strong>Noun</strong></p><ul><li>Pathology. acquired immune deficiency syndrome: a disease of the immune system characterized by increased susceptibility to opportunistic infections, as pneumocystis carinii pneumonia and candidiasis, to certain cancers, as Kaposi's sarcoma, and to neurological disorders: caused by a retrovirus and transmitted chiefly through blood or blood products that enter the body's bloodstream, especially by sexual contact or contaminated hypodermic needles.</li></ul>