mumble
verb [ I or T ] uk/ˈmʌm.bəl/ us/ˈmʌm.bəl/
B2 含糊地说，咕哝
to speak quietly and in a way that is not clear so that the words are difficult to understand
She mumbled something about being too busy. 她嘟囔着说太忙了。
[ + speech ] "I'm sorry," he mumbled. “我很抱歉，”他咕哝道。