The Collaborative International Dictionary of English v.0.48:

Disease \Dis*ease"\, n. [OE. disese, OF. desaise; des- (L. dis-)
   + aise ease. See Ease.]
   1. Lack of ease; uneasiness; trouble; vexation; disquiet.
      [Obs.]
      [1913 Webster]

            So all that night they passed in great disease.
                                                  --Spenser.
      [1913 Webster]

            To shield thee from diseases of the world. --Shak.
      [1913 Webster]

   2. An alteration in the state of the body or of some of its
      organs, interrupting or disturbing the performance of the
      vital functions, and causing or threatening pain and
      weakness; malady; affection; illness; sickness; disorder;
      -- applied figuratively to the mind, to the moral
      character and habits, to institutions, the state, etc.
      [1913 Webster]

            Diseases desperate grown,
            By desperate appliances are relieved. --Shak.
      [1913 Webster]

            The instability, injustice, and confusion introduced
            into the public counsels have, in truth, been the
            mortal diseases under which popular governments have
            every where perished.                 --Madison.
      [1913 Webster]

   Disease germ. See under Germ.

   Syn: Distemper; ailing; ailment; malady; disorder; sickness;
        illness; complaint; indisposition; affection. --
        Disease, Disorder, Distemper, Malady,
        Affection. Disease is the leading medical term.
        Disorder mean? much the same, with perhaps some slight
        reference to an irregularity of the system. Distemper is
        now used by physicians only of the diseases of animals.
        Malady is not a medical term, and is less used than
        formerly in literature. Affection has special reference
        to the part, organ, or function disturbed; as, his
        disease is an affection of the lungs. A disease is
        usually deep-seated and permanent, or at least
        prolonged; a disorder is often slight, partial, and
        temporary; malady has less of a technical sense than the
        other terms, and refers more especially to the suffering
        endured. In a figurative sense we speak of a disease
        mind, of disordered faculties, and of mental maladies.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Disease \Dis*ease"\, v. t. [imp. & p. p. Diseased; p. pr. &
   vb. n. Diseasing.]
   1. To deprive of ease; to disquiet; to trouble; to distress.
      [Obs.]
      [1913 Webster]

            His double burden did him sore disease. --Spenser.
      [1913 Webster]

   2. To derange the vital functions of; to afflict with disease
      or sickness; to disorder; -- used almost exclusively in
      the participle diseased.
      [1913 Webster]

            He was diseased in body and mind.     --Macaulay.
      [1913 Webster]

WordNet (r) 3.0 (2006):

disease
    n 1: an impairment of health or a condition of abnormal
         functioning

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "disease":
   affection, affliction, ailment, bane, blight, bug, bugbear, burden,
   calamity, cancer, complaint, condition, contagion, contaminate,
   crushing burden, curse, death, debility, decrepitude, destruction,
   disability, disorder, epizootic, evil, feebleness, grievance, harm,
   ill, illness, infect, infection, infirmity, infliction, malady,
   malaise, misery, murrain, nemesis, open wound, pest, pestilence,
   plague, running sore, scourge, sickliness, sickness, syndrome,
   taint, thorn, torment, unhealthiness, vexation, virus, visitation,
   woe