Source : Webster's Revised Unabridged Dictionary (1913)

Soundless \Sound"less\, a.
   Not capable of being sounded or fathomed; unfathomable.
   --Shak.

Soundless \Sound"less\, a.
   Having no sound; noiseless; silent. -- {Sound"less*ly}, adv.
   -- {Sound"less*ness}, n.

Source : WordNet®

soundless
     adj : marked by absence of sound; "a silent house"; "soundless
           footsteps on the grass"; "the night was still" [syn: {silent},
            {still}]