The Collaborative International Dictionary of English v.0.48:

Inexactitude \In`ex*act"i*tude\, n.
   1. Inexactness; uncertainty; as, geographical inexactitude.
      [1913 Webster]

   2. Something inexact; an instance of an inexact statement,
      measurement, etc.; as, in two minutes the senator has
      produced a dozen inexactitudes.
      [PJC]

WordNet (r) 3.0 (2006):

inexactitude
    n 1: the quality of being inaccurate and having errors [syn:
         inexactness, inexactitude] [ant: exactitude,
         exactness]