The Collaborative International Dictionary of English v.0.48:

Ailment \Ail"ment\, n.
   Indisposition; morbid affection of the body; -- not applied
   ordinarily to acute diseases. "Little ailments."
   --Landsdowne.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ailment
    n 1: an often persistent bodily disorder or disease; a cause for
         complaining [syn: ailment, complaint, ill]

Moby Thesaurus II by Grady Ward, 1.0:

80 Moby Thesaurus words for "ailment":
   abnormality, acute disease, affection, affliction,
   allergic disease, allergy, atrophy, bacterial disease,
   birth defect, blight, cardiovascular disease, chronic disease,
   circulatory disease, complaint, complication, condition,
   congenital defect, defect, deficiency disease, deformity,
   degenerative disease, disability, disease, disorder, disquiet,
   disquietude, distemper, endemic, endemic disease,
   endocrine disease, epidemic disease, ferment, functional disease,
   fungus disease, gastrointestinal disease, genetic disease,
   handicap, hereditary disease, iatrogenic disease, ill, illness,
   indisposition, infectious disease, infirmity, inquietude, malady,
   malaise, morbidity, morbus, muscular disease, neurological disease,
   nutritional disease, occupational disease, organic disease,
   pandemic disease, pathological condition, pathology, plant disease,
   protozoan disease, psychosomatic disease, queasiness,
   respiratory disease, restiveness, restlessness, rockiness,
   secondary disease, seediness, sickishness, sickness, signs,
   symptomatology, symptomology, symptoms, syndrome, the pip, turmoil,
   urogenital disease, virus disease, wasting disease, worm disease