The Collaborative International Dictionary of English v.0.48:

Abnormality \Ab`nor*mal"i*ty\, n.; pl. Abnormalities.
   1. The state or quality of being abnormal; variation;
      irregularity. --Darwin.
      [1913 Webster]

   2. Something abnormal.
      [1913 Webster]

WordNet (r) 3.0 (2006):

abnormality
    n 1: an abnormal physical condition resulting from defective
         genes or developmental deficiencies [syn: abnormality,
         abnormalcy] [ant: normalcy, normality]
    2: retardation sufficient to fall outside the normal range of
       intelligence [syn: abnormality, mental defectiveness]
    3: marked strangeness as a consequence of being abnormal [syn:
       abnormality, freakishness]
    4: behavior that breaches the rule or etiquette or custom or
       morality [syn: abnormality, irregularity]

Moby Thesaurus II by Grady Ward, 1.0:

214 Moby Thesaurus words for "abnormality":
   aberrance, aberrancy, aberration, acute disease, affection,
   affliction, ailment, alienation, allergic disease, allergy,
   anomaly, atrophy, bacterial disease, birth defect, blight,
   brain damage, brainsickness, cardiovascular disease,
   chronic disease, circulatory disease, clouded mind, complaint,
   complication, conceit, condition, congenital defect,
   conversation piece, crackpotism, crank, crankiness, crankism,
   craziness, criminality, crotchet, crotchetiness, curio, curiosity,
   daftness, defect, deficiency disease, deformity,
   degenerative disease, delinquency, dementedness, dementia,
   derangement, deviance, deviancy, deviation, differentness,
   disability, disease, disorder, disorientation, distemper,
   distortion, distraction, divergence, dottiness, eccentricity,
   endemic, endemic disease, endocrine disease, epidemic disease,
   erraticism, erraticness, exception, folie, freakiness,
   freakishness, functional disease, fungus disease, furor,
   gastrointestinal disease, genetic disease, handicap,
   hereditary disease, iatrogenic disease, idiocrasy, idiosyncrasy,
   illegality, illness, improbability, improperness, impropriety,
   inadmissibility, inapplicability, inappositeness,
   inappropriateness, inaptitude, inaptness, incorrectness,
   indecorousness, indecorum, indisposition, infectious disease,
   infelicity, infirmity, infraction, insaneness, insanity,
   irrationality, irregularity, irrelevance, irrelevancy, kink,
   loss of mind, loss of reason, lunacy, madness, maggot,
   maladjustment, malady, malaise, malformation, mania, mannerism,
   mental deficiency, mental derangement, mental disease,
   mental disorder, mental disturbance, mental illness,
   mental instability, mental sickness, mesalliance, mind overthrown,
   mindsickness, misalliance, misjoinder, misjoining, mismatch,
   morbidity, morbus, muscular disease, museum piece,
   neurological disease, nonconformity, nonesuch, nutritional disease,
   occupational disease, oddity, oddness, organic disease,
   pandemic disease, pathological condition, pathology, peculiarity,
   pixilation, plant disease, possession, prodigiosity, prodigy,
   protozoan disease, psychosomatic disease, queerness, quip, quirk,
   quirkiness, rabidness, rarity, reasonlessness, respiratory disease,
   rockiness, secondary disease, seediness, senselessness,
   shattered mind, sick mind, sickishness, sickness, signs,
   sinfulness, singularity, strange thing, strangeness,
   symptomatology, symptomology, symptoms, syndrome, the pip, trick,
   twist, unbalance, unbalanced mind, uncommonness, unconformity,
   uncongeniality, unconventionality, unfitness, unfittingness,
   unlawfulness, unnaturalness, unrighteousness, unsaneness,
   unseemliness, unsound mind, unsoundness, unsoundness of mind,
   unsuitability, unusualness, urogenital disease, violation,
   virus disease, wasting disease, whim, whimsicality, whimsy,
   wickedness, witlessness, worm disease, wrong, wrongfulness,
   wrongness