Source : Webster's Revised Unabridged Dictionary (1913)

Inaccurately \In*ac"cu*rate*ly\, adv.
   In an inaccurate manner; incorrectly; inexactly.

Source : WordNet®

inaccurately
     adv : in an inaccurate manner; "this student works rather
           inaccurately and sloppily" [ant: {accurately}]