What does "addiction" mean?

Addiction: The state of being addicted; devotion; inclination. "His addiction was to courses vain." Shak. ADDISON'S DISEASE Ad"di*son's dis*ease". Etym: [Named from Thomas Addison, M. D., of London, who first described it.] (Med.) A morbid condition causing a peculiar brownish discoloration of the skin, and thought, at one time, to be due to disease of the suprarenal capsules (two flat triangular bodies covering the upper part of the kidneys), but now known not to be dependent upon this causes exclusively. It is usually fatal.