unattainable

from WordNet (r) 3.0 (2006)

unattainable
    adj 1: impossible to achieve; "an unattainable goal" [syn:
           {unachievable}, {unattainable}, {undoable},
           {unrealizable}]

from The Collaborative International Dictionary of English v.0.48

Unattainable \Unattainable\
   See {attainable}.

from Moby Thesaurus II by Grady Ward, 1.0

37 Moby Thesaurus words for "unattainable":
      beyond one, beyond reach, closed forever to, closed to,
      impenetrable, impervious, impracticable, impractical, inaccessible,
      infeasible, inoperable, insuperable, insurmountable, lost to,
      out of reach, too much for, un-come-at-able, unaccessible,
      unachievable, unapproachable, unavailable, uncompassable,
      undiscoverable, undoable, uneffectible, unfeasible, ungetatable,
      ungettable, unnegotiable, unobtainable, unperformable,
      unprocurable, unreachable, unrealizable, unsecurable,
      unsurmountable, unworkable