muttering

/ˈmʌtərɪŋ/
noun
  1. Quiet, unclear speech that is often hard to understand, especially when expressing dissatisfaction.
    • There was a low muttering from the audience after the announcement.
    • His constant muttering annoyed everyone in the library.
    • I could hear the muttering of people waiting in line.
adjective
  1. Speaking in a low, unclear voice, often showing annoyance or discontent.
    • A muttering crowd gathered outside the building.
    • The muttering customer left the store without buying anything.
    • She gave a muttering reply and turned away.