The Collaborative International Dictionary of English v.0.48:

Unuttered \Unuttered\
   See uttered.

WordNet (r) 3.0 (2006):

unuttered
    adj 1: not made explicit; "the unexpressed terms of the
           agreement"; "things left unsaid"; "some kind of unspoken
           agreement"; "his action is clear but his reason remains
           unstated" [syn: unexpressed, unsaid, unstated,
           unuttered, unverbalized, unverbalised, unvoiced,
           unspoken]

Moby Thesaurus II by Grady Ward, 1.0:

75 Moby Thesaurus words for "unuttered":
   arcane, cabalistic, censored, classified, close, closed, concealed,
   cryptic, dark, echoless, enigmatic, esoteric, hermetic, hidden,
   hush as death, hush-hush, hushed, implicit, implied, inaudible,
   inferred, latent, mousy, mysterious, noiseless, occult, quiescent,
   quiet, restricted, secret, silent, smothered, soundless, stifled,
   still, still as death, stilly, subaudible, suppressed, tacit,
   top secret, ulterior, unarticulated, unbreatheable, undeclared,
   under security, under wraps, understood, undisclosable,
   undisclosed, undivulgable, undivulged, unexpressed, unhearable,
   unmentioned, unproclaimed, unpronounced, unpublished, unrecorded,
   unrevealable, unrevealed, unsaid, unsounded, unspoken, unsung,
   untalked-of, untellable, untold, unutterable, unvocalized,
   unvoiced, unwhisperable, unwritten, whist, wordless