牢骚 (láo sāo): 不満

The workload kept growing heavier, yet his salary hadn't gone up in years, so Lao Zhang couldn't help grumbling a few complaints to his colleagues.

While picking up the toys her child had left scattered around, Mom kept grumbling that the house would never stay tidy.

At the meeting he didn't openly oppose the plan; he just quietly grumbled a few complaints that the budget was too small.

The tour bus was two hours late, and the tourists, standing in the sun and full of grievances, all demanded an explanation from the guide.

My older sister is always complaining to her friends that her boyfriend isn't attentive enough, but when it comes to actually breaking up, she can't bear to.