MUT'TER, verb intransitive [Latin mutio, muttio, and musso, mussito; allied perhaps to muse, which see.] 1. To utter words with a low voice and compressed lips, with sullenness or in complaint; to grumble; to murmur. Meantime your filthy foreigner will stare, And mutter to himself. 2. To sound with a low rumbling noise. Thick lightnings flash, the muttering thunder rolls. MUT'TER, verb transitive To utter with imperfect articulations, or with a low murmuring voice. Your lips have spoken lies, your tongue hath muttered perverseness. Isaiah 59:3. They in sleep will mutter their affairs. MUT'TER, noun Murmur; obscure utterance.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI