The Collaborative International Dictionary of English v.0.48:

Inaccuracy \In*ac"cu*ra*cy\, n.; pl. Inaccuracies.
   [1913 Webster]
   1. The quality of being inaccurate; lack of accuracy or
      exactness.
      [1913 Webster]

   2. That which is inaccurate or incorrect; mistake; fault;
      defect; error; as, in inaccuracy in speech, copying,
      calculation, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

inaccuracy
    n 1: the quality of being inaccurate and having errors [ant:
         accuracy, truth]

Moby Thesaurus II by Grady Ward, 1.0:

105 Moby Thesaurus words for "inaccuracy":
   abstractionism, adulteration, allowance, amorphousness,
   approximation, blobbiness, blurriness, broadness, coloring,
   defectibility, defectiveness, deficiency, deformation, deviation,
   disorder, distortion, erroneousness, exaggeration, expressionism,
   fallibility, false coloring, falsification, faultiness, fogginess,
   fuzziness, garbling, generality, haziness, hyperbole,
   ill-definedness, immaturity, impairment, imperfection, imprecision,
   impurity, inaccurateness, inadequacy, inadequateness, inchoateness,
   incoherence, incompleteness, incorrectness, indecisiveness,
   indefinableness, indefiniteness, indeterminateness, indistinctness,
   inexactitude, inexactness, injustice, lack, laxity, litotes,
   looseness, mediocrity, miscoloring, misdrawing, mispainting,
   misquotation, misreport, misrepresentation, misstatement,
   misteaching, mistiness, negligence, nonrealism, obscuration,
   obscurity, overdrawing, overstatement, patchiness, perversion,
   predictable error, probable error, shapelessness, shortage,
   shortcoming, sketchiness, slanting, standard deviation,
   sweepingness, tolerance, twisting, unclearness,
   unconscientiousness, uncorrectness, uncriticalness, understatement,
   undevelopment, unevenness, unexactingness, unfactualness,
   unfinicalness, unfussiness, unmeticulousness, unparticularness,
   unperfectedness, unpreciseness, unpunctiliousness, unpunctuality,
   unrigorousness, unscrupulousness, unsoundness, vagueness, want