The Collaborative International Dictionary of English v.0.48:
Inexactness \In`ex*act"ness\, n. Incorrectness; lack of exactness. [1913 Webster]WordNet (r) 3.0 (2006):
inexactness n 1: the quality of being inaccurate and having errors [syn: inexactness, inexactitude] [ant: exactitude, exactness]