* Whispered
* Grumbled
* mumbled
* Sputtered
* Stammered
Here are some examples of how "muttered" can be used:
* "He muttered something about being too tired to go out."
* "She muttered a curse under her breath."
* "The old man muttered about the good old days."
The word "muttered" can also be used to describe a low, indistinct sound:
* "The wind muttered through the trees."
* "The machine muttered and sputtered as it started up."