Webster’s Revised Unabridged Dictionary · 1913
Mutter
Mut′ter (mŭt′tẽr), v. i. [imp. & p. p. Muttered; p. pr. & vb. n. Muttering.] [Prob. of imitative origin; cf. L. muttire, mutire.] 1. 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.
Wizards that peep, and that mutter. Is. viii. 19.
Meantime your filthy foreigner will stare, And mutter to himself. Dryden.
2. To sound with a low, rumbling noise.
Thick lightnings flash, the muttering thunder rolls. Pope.
Mut′ter, v. t. To utter with imperfect articulations, or with a low voice; as, to mutter threats. Shak.
Mut′ter, n. Repressed or obscure utterance.