They knitted their brows and started to grumble.他们皱着眉头开始抱怨起来。We used to grumble that we were wasting time learning a dead language.我们过去常常抱怨自己是在浪费时间学一门死语言。It's simply not in her nature to grumble.发牢骚可不是她的本性。She began to grumble within his hearing.她开始在他耳边抱怨。