grumbling

She was grumbling about the long line at the grocery store.

The employees were grumbling about the new overtime policy.

He was grumbling under his breath about the slow service.

The students were grumbling about the amount of homework they had.

She couldn't help grumbling about the noisy neighbors.

The passengers were grumbling about the delayed flight.

He was grumbling about having to work on the weekend.

The customers were grumbling about the high prices.

She was grumbling about the cold weather.

The players were grumbling about the referee's calls.