He mumbled a few words and left.

他咕哝了几便走了。

I wish you wouldn't mumble - I can't hear you clearly.

我希望你说话不要含含糊糊 - 我听不清你在讲什么。

He mumbled something to me which I did not quite catch.

他对我叽咕了几话, 我没太听清楚。

He mumbled sth. to me but I could not hear what he said.

他对我咕哝了几，我没听清他说的什么。

Mr. Bosher, with his mouthful of biscuit, mumbled that it was sweetly pretty.

伯希尔先生满嘴塞着饼干，叽叽咕咕地说这真美极了。

He always mumbles when he's embarrassed.

他感到难为情时说话就含糊不清了。

George mumbled incoherently to himself.

乔治语无伦次地喃喃自语。

In March he goes on a survival course and learns about the “umbles”: as hypothermia sets in you mumble, fumble, grumble, stumble, then finally tumble.

三月，开始野外生存训练，懂得了寒冷下嘴、脚什么样：低温开始了，咕哝，摸爬，嘟囔，踉跄，终于仆倒在地。