grumble

(noun) a loud low dull continuous noise. Synonyms: rumble, rumbling, grumbling. Examples: "They heard the rumbling of thunder."

(noun) a complaint uttered in a low and indistinct tone. Synonyms: grumbling, murmur, murmuring, mutter, muttering.

(verb) show one's unhappiness or critical attitude. Synonyms: grouch, scold. Examples: "He scolded about anything that he thought was wrong." "We grumbled about the increased work load."

(verb) make complaining remarks or noises under one's breath. Synonyms: murmur, mutter, croak, gnarl. Examples: "She grumbles when she feels overworked."

(verb) to utter or emit low dull rumbling sounds. Synonyms: growl, rumble. Examples: "He grumbled a rude response." "Stones grumbled down the cliff."

(verb) make a low noise. Synonyms: rumble. Examples: "Rumbling thunder."