immune

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Not subject to an obligation imposed on others; exempt.
• adjective Having legal immunity.
• adjective Not affected by a given influence; unresponsive.
• adjective Of or relating to immunity or an immune response.
• adjective Having resistance to a specific pathogen.
• adjective Having or producing sensitized antibodies or lymphocytes that react to specific antigens.

from The Century Dictionary.

• Exempt; specifically, protected by inoculation: as, an immune animal.
• noun One who is exempt; specifically, one who is protected from a particular disease by inoculation or by a previous attack.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who is immune; esp., a person who is immune from a disease by reason of previous affection with the disease or inoculation.
• adjective Exempt; protected.
• adjective (Med.) Protected from disease due to the action of the immune system, especially by having been inoculated against or previously exposed to a disease.
• adjective (Med.) Of or pertaining to the immune system or the components of the immune system.
• adjective Not responsive.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective usually with "from" Exempt; not subject to
• adjective medicine, usually with "to" Protected by inoculation, or due to innate resistance to pathogens
• adjective by extension Not vulnerable
• adjective medicine Of or pertaining to the immune system
• noun epidemiology A person who is not susceptible to infection by a particular disease

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective (usually followed by `to') not affected by a given influence
• adjective relating to the condition of immunity
• adjective secure against
• adjective relating to or conferring immunity (to disease or infection)
• noun a person who is immune to a particular infection