資料來源 : Webster's Revised Unabridged Dictionary (1913)

Noiseless \Noise"less\, a.
   Making, or causing, no noise or bustle; without noise;
   silent; as, the noiseless foot of time.

         So noiseless would I live.               --Dryden.
   -- {Noise"less*ly}, adv. -- {Noise"less*ness}, n.

資料來源 : WordNet®

noiselessness
     n : the property of making no noise