Definition of mutter

• v. i. - To utter words indistinctly or with a low voice and lips partly closed; esp., to utter indistinct complaints or angry expressions; to grumble; to growl.
• v. i. - To sound with a low, rumbling noise.
• v. t. - To utter with imperfect articulations, or with a low voice; as, to mutter threats.
• n. - Repressed or obscure utterance.