Biology A physiological reaction of an organism used in self-protection, as against infection.
Psychology Any of various usually unconscious mental processes, including denial, projection, rationalization, and repression, that protect the ego from shame, anxiety, conflict, loss of self-esteem, or other unacceptable feelings or thoughts.
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.