grumble in WordNet English dictionary

1. make complaining remarks or noises under one's breath
   "she grumbles when she feels overworked"
   murmur  mutter  grumble  croak  gnarl 
   
2. show one's unhappiness or critical attitude
   "He scolded about anything that he thought was wrong"; "We grumbled about the increased work load"
   grouch  grumble  scold 
   
3. to utter or emit low dull rumbling sounds
   "he grumbled a rude response"; "Stones grumbled down the cliff"
   grumble  growl  rumble 
   
4. make a low noise
   "rumbling thunder"
   rumble  grumble 
   

1. a complaint uttered in a low and indistinct tone
   grumble  grumbling  murmur  murmuring  mutter  muttering 
   
2. a loud low dull continuous noise
   "they heard the rumbling of thunder"
   rumble  rumbling  grumble  grumbling