| Noun | 1. | acquired immunity - immunity to a particular disease that is not innate but has been acquired during life; immunity can be acquired by the development of antibodies after an attack of an infectious disease or by a pregnant mother passing antibodies through the placenta to a fetus or by vaccinationimmunity, resistance - (medicine) the condition in which an organism can resist disease active immunity - a form of acquired immunity in which the body produces its own antibodies against disease-causing antigens passive immunity - an impermanent form of acquired immunity in which antibodies against a disease are acquired naturally (as through the placenta to an unborn child) or artificially (as by injection of antiserum) |