to complain in a low voice

to mutter or speak in a low voice

बड़बड़ाना

English Usage: He would grumble under his breath whenever he had to do extra work.

Hindi Usage: जब भी उसे अतिरिक्त काम करना पड़ता, वह बड़बड़ाता रहता.

a complaint or expression of dissatisfaction

शिकायत

English Usage: His constant grumble about the weather annoyed everyone.

Hindi Usage: मौसम के बारे में उसकी लगातार शिकायत सबका मन खराब कर देती थी.