Source : Webster's Revised Unabridged Dictionary (1913)

Addison's disease \Ad"di*son's dis*ease"\ [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.

Source : WordNet®

Addison's disease
     n : a glandular disorder caused by failure of function of the
         cortex of the adrenal gland and marked by anemia and
         prostration with brownish skin [syn: {Addison's syndrome},
          {hypoadrenalism}, {hypoadrenocorticism}]