The Collaborative International Dictionary of English v.0.48:

Impractical \Im*prac"ti*cal\, a.
   Not practical.
   [1913 Webster]

WordNet (r) 3.0 (2006):

impractical
    adj 1: not practical; not workable or not given to practical
           matters; "refloating the ship proved impractical because
           of the expense"; "he is intelligent but too impractical
           for commercial work"; "an impractical solution" [ant:
           practical]
    2: not practical or realizable; speculative; "airy theories
       about socioeconomic improvement"; "visionary schemes for
       getting rich" [syn: airy, impractical, visionary,
       Laputan, windy]

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "impractical":
   abstract, academic, airy, armchair, autistic, awkward, beyond one,
   bulky, clumsy, conjectural, contrary, crosswise, cumbersome,
   dereistic, hulking, hulky, hypothetic, ideal, idealistic,
   impracticable, in the clouds, inconvenient, ineffective,
   ineffectual, infeasible, inoperable, insuperable, insurmountable,
   moot, nonfunctional, nonrealistic, notional, otherworldly,
   perverse, poetic, ponderous, postulatory, quixotic, romancing,
   romantic, romanticized, speculative, starry, starry-eyed,
   storybook, theoretical, too much for, transcendental, transmundane,
   unachievable, unattainable, unavailing, uncompassable, undoable,
   uneffectible, unfeasible, unhandy, unmanageable, unnegotiable,
   unperformable, unpractical, unrealistic, unrealizable,
   unserviceable, unsurmountable, unusable, unwieldy, unworkable,
   useless, visionary, wild, wish-fulfilling