Meaning of mutter

mut•ter

1. to utter words indistinctly or in a low tone, often as if talking to oneself; murmur.
2. to complain murmuringly; grumble.
3. to make a low, rumbling sound.

1. to utter indistinctly or in a low tone: to mutter complaints.

1. the act or utterance of a person who mutters.