Source : Webster's Revised Unabridged Dictionary (1913)

Impracticably \Im*prac"ti*ca*bly\, adv.
   In an impracticable manner.

         Morality not impracticably rigid.        --Johnson.

Source : WordNet®

impracticably
     adv : to an impracticable degree; "this is still impracticably
           high"