Source : Webster's Revised Unabridged Dictionary (1913)

Murmur \Mur"mur\, n. [F. murmure: cf. L. murmur. CF. {Murmur},
   v. i.]
   1. A low, confused, and indistinct sound, like that of
      running water.

   2. A complaint half suppressed, or uttered in a low,
      muttering voice. --Chaucer.

            Some discontents there are, some idle murmurs.
                                                  --Dryden.

Murmur \Mur"mur\, v. i. [imp. & p. p. {Murmured}; p. pr. & vb.
   n. {Murmuring}.] [F. murmurer, L. murmurare, murmurari, fr.
   murmur murmur; cf. Gr.? to roar and boil, said of water, Skr.
   marmara a rustling sound; prob. of imitative origin.]
   1. To make a low continued noise, like the hum of bees, a
      stream of water, distant waves, or the wind in a forest.

            They murmured as doth a swarm of bees. --Chaucer.

   2. To utter complaints in a low, half-articulated voice; to
      feel or express dissatisfaction or discontent; to grumble;
      -- often with at or against. ``His disciples murmured at
      it.'' --John vi. 61.

            And all the children of Israel murmured against
            Moses and against Aaron.              --Num. xiv. 2.

            Neither murmur ye, as some of them also murmured.
                                                  --1 Cor. x.
                                                  10.

Murmur \Mur"mur\, v. t.
   To utter or give forth in low or indistinct words or sounds;
   as, to murmur tales. --Shak.

         The people murmured such things concerning him. --John
                                                  vii. 32.

Source : WordNet®

murmur
     v 1: speak softly or indistinctly; "She murmured softly to the
          baby in her arms"
     2: make complaining remarks or noises under one's breath; "she
        grumbles when she feels overworked" [syn: {mutter}, {grumble},
         {croak}, {gnarl}]

murmur
     n 1: a low continuous indistinct sound; often accompanied by
          movement of the lips without the production of
          articulate speech [syn: {mutter}, {muttering}, {murmuring},
           {murmuration}, {mussitation}]
     2: a schwa that is incidental to the pronunciation of a
        consonant [syn: {murmur vowel}]
     3: an abnormal sound of the heart; sometimes a sign of abnormal
        function of the heart valves [syn: {heart murmur}, {cardiac
        murmur}]
     4: a complaint uttered in a low and indistinct tone [syn: {grumble},
         {grumbling}, {murmuring}, {mutter}, {muttering}]