The Collaborative International Dictionary of English v.0.48:

Unshaken \Unshaken\
   See shaken.

WordNet (r) 3.0 (2006):

unshaken
    adj 1: unshaken in purpose; "wholly undismayed by the commercial
           failure of the three movies he had made" [syn:
           undaunted, undismayed, unshaken]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "unshaken":
   abiding, calm, constant, coolheaded, failing, firm, fixed, flinty,
   going strong, immovable, in full force, in full swing, inexcitable,
   inflexible, loyal, nerveless, never, relaxed, rock-steady, set,
   settled, sot, staunch, steadfast, steady, steady-handed,
   steady-nerved, steel-nerved, steely, strong-nerved, true, unabated,
   unallayed, unbated, unbending, unblenching, unblinking,
   undeflectable, undiminished, unexhausted, unfaded, unfaltering,
   unflagging, unflappable, unflinching, unnervous, unquestioning,
   unquivering, unshaky, unshrinking, unstrained, unswerving,
   untremulous, unwavering, unweakened, unweakening, unwithered,
   unworn, unyielding, without a tremor