Mutter

v. i.	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. [imp. & p. p. Muttered ; p. pr. & vb. n. Muttering.] 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.
v. t.	1.	To utter with imperfect articulations, or with a low voice; as, to mutter threats.
n.	1.	Repressed or obscure utterance.

Noun	1.	mutter - a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech Synonyms: murmur, murmuration, murmuring, mussitation, muttering
	2.	mutter - a complaint uttered in a low and indistinct tone Synonyms: grumble, grumbling, murmuring, muttering, murmur
Verb	1.	mutter - talk indistinctly; usually in a low voice Synonyms: mumble, mussitate, maunder
	2.	mutter - make complaining remarks or noises under one's breath; "she grumbles when she feels overworked" Synonyms: gnarl, grumble, murmur, croak

mutter - To quietly enter a command not meant for the ears, eyes, or fingers of ordinary mortals. Often used in "mutter an incantation". See also wizard.

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, 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, 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, whispering, whistle, yap, yawp, yell, yelp, yowl