Definition: to speak too quietly and not clearly enough for someone to understand you Level: B2
他咕哝着说不想出去。
He ___mumbled that he wasn't interested in going out.
她含糊地道了个歉，迅速离开了房间。
She ___mumbled an apology and quickly left the room.
别咕咕哝哝的，说清楚点，这样我才能听懂！
Stop ___mumbling and speak clearly so I can understand you!
