Dictionary.net

complain quietly

show one's unhappiness or critical attitude; "He scolded about anything that he thought was wrong"; "We grumbled about the increased work load"

to utter or emit low dull rumbling sounds; "he grumbled a rude response"; "Stones grumbled down the cliff"

show one's unhappiness or critical attitude; "He scolded about anything that he thought was wrong"; "We grumbled about the increased work load"

make complaining remarks or noises under one's breath; "she grumbles when she feels overworked"

to utter or emit low dull rumbling sounds; "he grumbled a rude response"; "Stones grumbled down the cliff"

To murmur or mutter with discontent; to make ill-natured complaints in a low voice and a surly manner.

To growl; to snarl in deep tones; as, a lion grumbling over his prey.

To rumble; to make a low, harsh, and heavy sound; to mutter; as, the distant thunder grumbles.

To express or utter with grumbling.

The noise of one that grumbles.

A grumbling, discontented disposition.

To murmur or mutter with discontent; to make ill-natured complaints in a low voice and a surly manner.

To growl; to snarl in deep tones; as, a lion grumbling over his prey.

To rumble; to make a low, harsh, and heavy sound; to mutter; as, the distant thunder grumbles.

To express or utter with grumbling.

The noise of one that grumbles.

A grumbling, discontented disposition.

To murmur discontentedly; growl; rumble; find fault.

To murmur with discontent: to growl: to rumble.

GRUMBLINGLY.

To murmur with discontent; growl.

The act of grumbling; a complaint; murmur.

Grumbling.