The Collaborative International Dictionary of English v.0.48:

Inaccurate \In*ac"cu*rate\, a.
   Not accurate; not according to truth; inexact; not quite
   correct; incorrect; erroneous; as, in inaccurate man,
   narration, copy, judgment, calculation, etc.

   Note: The term inaccurate is usually used when an assertion
         or result is near to the truth, but not exactly, or has
         some basis for belief; however, it is sometimes used as
         a gentle euphemism for wrong even if the error is
         flagrant.
         [1913 Webster +PJC]

               The expression is plainly inaccurate. --Bp. Hurd.

   Syn: Inexact; incorrect; erroneous; faulty; imperfect;
        incomplete; defective.
        [1913 Webster]

WordNet (r) 3.0 (2006):

inaccurate
    adj 1: not exact; "an inaccurate translation"; "the thermometer
           is inaccurate" [ant: accurate]