WordNet (r) 3.0 (2006):

unimpaired
    adj 1: not damaged or diminished in any respect; "his speech
           remained unimpaired" [ant: impaired]

Moby Thesaurus II by Grady Ward, 1.0:

38 Moby Thesaurus words for "unimpaired":
   bright, entire, fresh, harmless, intact, inviolate, mint, perfect,
   pristine, scatheless, sound, unbroken, unbruised, undamaged,
   undefaced, undeformed, undemolished, undestroyed, unfaded,
   unharmed, unhurt, uninjured, unmaimed, unmangled, unmarked,
   unmarred, unscarred, unscathed, unscratched, unshattered,
   unspoiled, untorn, untouched, unwithered, unworn, virgin, whole,
   wholesome