The Collaborative International Dictionary of English v.0.48:

Unheard \Un*heard"\, a.
   1. Not heard; not perceived by the ear; as, words unheard by
      those present.
      [1913 Webster]

   2. Not granted an audience or a hearing; not allowed to
      speak; not having made a defense, or stated one's side of
      a question; disregarded; unheeded; as, to condem? a man
      unheard.
      [1913 Webster]

            What pangs I feel, unpitied and unheard! --Dryden.
      [1913 Webster]

   3. Not known to fame; not illustrious or celebrated; obscure.
      [1913 Webster]

            Nor was his name unheard or unadored. --Milton.
      [1913 Webster]

   Unheard of.
      (a) Not heard of; of which there are no tidings.
      (b) Unknown to fame; obscure. --Glanvill.
          [1913 Webster]

WordNet (r) 3.0 (2006):

unheard
    adj 1: not necessarily inaudible but not heard