William went away muttering to himself.

威廉喃喃自语地走了。

《柯林斯英汉双解大词典》

He continued walking back and forth, muttering to himself; he had forgotten the King entirely.

他不断地走来走去，喃喃自语；他完全忘记了国王。

youdao

He sat there shaking his head, muttering to himself.

他坐在那儿摇着头，自言自语地嘀咕着。

youdao

Viana was saying something, not in a whisper now, but as if muttering to himself.

NEWYORKER: While the Women Are Sleeping

Nothing matters to Tony except inventing things and having a good time, and Downey, muttering to himself, ignores everyone else in the movie for as long as he can.

NEWYORKER: Iron Man

Dr. Ferrara joined Genentech as a junior scientist in 1988, and his colleagues were charmed by the slightly disheveled Sicilian who drove to work on his Yamaha VMAX motorcycle and paced the hallways, muttering to himself, when his work was going well.

FORBES: The Single-Minded Sleuth