mumble

含糊地說、咕噥、喃喃而語

He mumbled an apology and hurried out of the room.

他含糊地道了個歉，就匆匆走出房間。

低聲自語、喃喃自語

She kept mumbling to herself while looking for her keys.

她一邊找鑰匙，一邊不停地低聲自語。

含糊的話、咕噥聲

His answer was just a mumble that nobody could understand.

他的回答只是一句誰都聽不懂的含糊話語。