a loud low dull continuous noise; "they heard the rumbling of thunder"
a complaint uttered in a low and indistinct tone
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"
make a low noise; "rumbling thunder"