the ability of an organism to resist disease, either through the activities of specialized blood cells or antibodies produced by them in response to natural exposure or inoculation (active immunity) or by the injection of antiserum or the transfer of antibodies from a mother to her baby via the placenta or breast milk (passive immunity)

freedom from obligation or duty, esp exemption from tax, duty, legal liability, etc

any special privilege granting immunity

the exemption of ecclesiastical persons or property from various civil obligations or liabilities