1mum·ble 
/ˈmʌmbəl/ verb
mum·bles; mum·bled; mum·bling /ˈmʌmbəl/ verb : to say (something) quietly in an unclear way that makes it difficult for people to know what you said [+ obj] ▪ He mumbled something and then left. ▪ He mumbled “Goodbye” and then left. [no obj] ▪ I can't understand you when you mumble. ▪ a mumbling response
— mum·bler /ˈmʌmbəlɚ/ noun, plural mum·blers [count]
/ˈmʌmbəlɚ/ noun, plural mum·blers [count]— mumbling noun, plural mumblings [count, noncount]
▪ There were mumblings [=rumblings] (of discontent) about the decision. [=people complained quietly to each other about the decision]
▪ There were mumblings [=rumblings] (of discontent) about the decision. [=people complained quietly to each other about the decision]
