mutter

verb
1
to speak or say something in a quiet voice that is difficult to hear, especially because you are annoyed about something
زمزمه کردن, غرغر کردن, زیرلب گفتن, زیرلب غر زدن
2
to complain about something, without saying publicly what you think
غرغر کردن, زیر لب گله کردن, زیر لبی شکایت کردن, نق زدن
Workers continued to mutter about the management.
A number of non-British visitors were heard to mutter that it would not have happened in Frankfurt.
synonym grumble
noun
1
a quiet sound or words that are difficult to hear
زمزمه