The Collaborative International Dictionary of English v.0.48:

Voiceless \Voice"less\, a.
   1. Having no voice, utterance, or vote; silent; mute; dumb.
      [1913 Webster]

            I live and die unheard,
            With a most voiceless thought, sheathing it as a
            sword.                                --Byron.
      [1913 Webster]

   2. (Phon.) Not sounded with voice; as, a voiceless consonant;
      surd.
      [1913 Webster]

   Voiceless stop (Phon.), a consonant made with no audible
      sound except in the transition to or from another sound; a
      surd mute, as p, t, k.
      [1913 Webster] -- Voice"less*ly, adv. --
      Voice"less*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

voicelessness
    n 1: a disorder of the vocal organs that results in the loss of
         voice [syn: aphonia, voicelessness]
    2: speaking softly without vibration of the vocal cords [syn:
       whisper, whispering, susurration, voicelessness]
    3: having no voice in the management or control of affairs; "the
       voicelessness of those who live in situations of
       hopelessness"