To speak indistinctly in low tones.(verb-intransitive)
To complain or grumble morosely.(verb-intransitive)
To utter or say in low indistinct tones.(verb-transitive)
A low grumble or indistinct utterance.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "mutter" in a sentence
"I don't think that what "W" has to mutter is worth much."
"How can I parse this strange Arcadian Death, in mutter of oath, in rhyme of breath?"
"Can't remember, I'll have to check on that ... damn seive brain ... mutter mutter mutter ..."