Definition of: mutter

(mut′ər) v.i.
1. To speak in a low, indistinct tone and with compressed lips, as in complaining or talking to oneself.
2. To complain; grumble.
3. To make a low, rumbling sound.
—v.t.
4. To say in a low, indistinct tone.
—noun An imperfect utterance; murmur. [Prob. imit. Cf. dial. G muttern and L muttire.]
—mut′ter·er noun
—mut′ter·ing noun & adjective
—mut′ter·ing·ly adverb