Synonyms of mutter in English:

mutter


See US English definition of mutter

See UK English definition of mutter

See Spanish definition of mascullar

verb

1‘a group of men stood muttering in one corner of the room’

SYNONYMS
talk under one's breath, murmur, mumble, whisper, speak in an undertone, speak sotto voce, speak in hushed tones
talk to oneself
ANTONYMS

speak out

2‘backbenchers muttered about the reshuffle’

SYNONYMS
grumble, moan, complain, grouse, carp, whine, bleat
Northern English mither, twine
informal gripe, beef, bitch, sound off
British informal whinge, chunter, grizzle
North American informal kvetch