mutter (
http://definr.com/mutter)
n 1: a low continuous indistinct sound; often accompanied by
movement of the lips without the production of
articulate speech [syn:
muttering,
murmur,
murmuring,
murmuration,
mussitation]
2: a complaint uttered in a low and indistinct tone [syn:
grumble,
grumbling,
murmur,
murmuring,
muttering]
v 1: talk indistinctly; usually in a low voice [syn:
mumble,
maunder,
mussitate]
2: complain quietly [syn:
murmur,
grumble,
croak,
gnarl]