He mumbled a few words and left.

他咕哝了几句便走了。

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

希望你含含糊糊 - 听清你在讲什么。

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

他对叽咕了几句, 可没太听清楚。

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

他对咕哝了几句，可是没听清他的什么。

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

伯希尔先生满嘴塞着饼干，叽叽咕咕真是美极了。

He always mumbles when he's embarrassed.

他感到难为情时就含糊清了。

George mumbled incoherently to himself.

乔治语无伦次喃喃自语。

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、脚是什么样：低温开始了，咕哝，摸爬，嘟囔，踉跄，终于仆倒在。