1. spoke in a low, unclear voice, often expressing dissatisfaction or complaint
Usage: past tense of ‘mutter’

Examples

• She muttered something under her breath when the teacher assigned more homework.
• He muttered complaints about the long wait in line.
• The student muttered the answer so quietly that no one could hear.
• She muttered angrily as she cleaned up the mess.
• He muttered a quick apology before walking away.
• The old man muttered to himself while reading the newspaper.