1. grumble, grumbling, rumble, rumbling

a loud low dull continuous noise

Example Sentences:
'they heard the rumbling of thunder'

• grumbling
• rumble
• rumbling

2. grumble, grumbling, murmur, murmuring, mutter, muttering

a complaint uttered in a low and indistinct tone

• grumbling
• murmur
• murmuring
• mutter
• muttering

3. grouch, grumble, scold

show one's unhappiness or critical attitude

Example Sentences:
'He scolded about anything that he thought was wrong'
'We grumbled about the increased work load'

• grouch
• scold

4. croak, gnarl, grumble, murmur, mutter

make complaining remarks or noises under one's breath

Example Sentences:
'she grumbles when she feels overworked'

• croak
• gnarl
• murmur
• mutter

5. growl, grumble, rumble

to utter or emit low dull rumbling sounds

Example Sentences:
'he grumbled a rude response'
'Stones grumbled down the cliff'

• growl
• rumble

6. grumble, rumble

make a low noise

Example Sentences:
'rumbling thunder'

• rumble