mutter under one's breath 低声嘀咕
mutter something 嘟囔某事
A: Did you hear what he said?
A：你听到他说了什么吗。
B: No, he just muttered something under his breath.
B：没有，他只是低声嘟囔了几句。
1) 低声说话
2) 嘀咕/抱怨
3) 含糊不清地表达
1. 嘀咕；低声说
verb
1. To speak in a low, quiet, and often indistinct way, especially when complaining.
Synonym: mumble, murmur