Mutter1. (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.
2. (v. i.) To sound with a low, rumbling noise.
3. (v. t.) To utter with imperfect articulations, or with a low voice; as, to mutter threats.
4. (n.) Repressed or obscure utterance.
Thesaurus Entries
air a grievance, aspirate, aspiration, bark, bated breath, bawl, beef, bellow, bellyache, bitch, blare, blat, blubber, boom, bray, breath, breathe, breathy voice, buzz, cackle, chant, chirp, clamor, complain, coo, crab, croak, crow, cry, dolorous tirade, drawl, drone, droning, exclaim, exhalation, flute, fret, fret and fume, fumble, fuss, gabble, gasp, gibber, gibbering, gripe, groan, grouch, grouse, growl, grumble, grunt, hiss, holler, howl, jabber, jeremiad, jibber, keen, kick, lament, lilt, little voice, lodge a complaint, low voice, maffle, maunder, maundering, moan, mouth, mouthing, muddle, mumble, mumbling, murmur, murmuration, murmuring, mussitate, muttering, outcry, pant, pipe, plaint, planctus, raise a howl, register a complaint, repine, roar, rumble, rumor, scold, scream, screech, shriek, sibilate, sigh, sing, snap, snarl, snort, sob, soft voice, sough, speak incoherently, splutter, sputter, squall, squawk, squeal, stage whisper, still small voice, susurrate, susurration, susurrus, swallow, take on, thunder, tirade, trumpet, twang, ululation, underbreath, undertone, wail, wail of woe, warble, whimper, whine, whisper, whispering, whistle, yap, yawp, yell, yelp, yowl