He mumbled a few words and left.

咕哝几句便走。

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

我希望你说话不要含含糊糊 - 我不清你在。

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

对我叽咕几句话, 可我没太清楚。

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

对我咕哝几句，可是我没清说的。

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

伯希尔先生满嘴塞着饼干，叽叽咕咕地说这真是美极。

He always mumbles when he's embarrassed.

到难为情时说话就含糊不清。

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，懂得寒冷下嘴、脚是样：低温开始，咕哝，摸爬，嘟囔，踉跄，终于仆倒在地。