grumbling

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

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

(verb) show one's unhappiness or critical attitude. Synonyms: grouch, grumble, 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, grumble, croak, gnarl. Examples: "She grumbles when she feels overworked."

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

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

(adj) continuous full and low-pitched throbbing sound. Synonyms: rumbling. Examples: "The rumbling rolling sound of thunder."