Source : Webster's Revised Unabridged Dictionary (1913)

Murmuration \Mur`mur*a"tion\, n. [L. murmuratio.]
   The act of murmuring; a murmur. [Obs.] --Skelton.

Source : WordNet®

murmuration
     n : a low continuous indistinct sound; often accompanied by
         movement of the lips without the production of articulate
         speech [syn: {mutter}, {muttering}, {murmur}, {murmuring},
          {mussitation}]