The Collaborative International Dictionary of English v.0.48:

Unpronounced \Unpronounced\
   See pronounced.

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "unpronounced":
   echoless, hush as death, hushed, inaudible, mousy, noiseless,
   quiescent, quiet, silent, soundless, still, still as death, stilly,
   subaudible, unarticulated, undeclared, unexpressed, unhearable,
   unmentioned, unproclaimed, unpublished, unrecorded, unsaid,
   unsounded, unspoken, unsung, untalked-of, untold, unuttered,
   unvocalized, unvoiced, unwritten, whist, wordless