The Collaborative International Dictionary of English v.0.48:
Impracticably \Im*prac"ti*ca*bly\, adv. In an impracticable manner. [1913 Webster] Morality not impracticably rigid. --Johnson. [1913 Webster]WordNet (r) 3.0 (2006):
impracticably adv 1: to an impracticable degree; "this is still impracticably high"