Source : Webster's Revised Unabridged Dictionary (1913)

Impracticability \Im*prac`ti*ca*bil"i*ty\, n.; pl.
   {Impracticabilities}.
   1. The state or quality of being impracticable;
      infeasibility. --Goldsmith.

   2. An impracticable thing.

   3. Intractableness; stubbornness.

Source : WordNet®

impracticability
     n : the quality of not being usable [syn: {impracticableness}]
         [ant: {practicability}, {practicability}]