The Collaborative International Dictionary of English v.0.48:

Undiminished \Undiminished\
   See diminished.

WordNet (r) 3.0 (2006):

undiminished
    adj 1: not lessened or diminished; "unrelieved suffering" [syn:
           undiminished, unrelieved]

Moby Thesaurus II by Grady Ward, 1.0:

41 Moby Thesaurus words for "undiminished":
   complete, developed, entire, full, full-fledged, full-grown,
   full-scale, global, going strong, in full force, in full swing,
   intact, mature, matured, ripe, solid, total, unabated,
   unabbreviated, unallayed, unbated, unclipped, uncropped, uncut,
   undivided, unexhausted, unexpurgated, unfaded, unflagging,
   unmitigated, unreduced, unrestricted, unretarded, unsevered,
   unshaken, unshorn, unweakened, unweakening, unwithered, unworn,
   whole