Mumble

To speak with the lips partly closed, so as to render the sounds inarticulate and imperfect; to utter words in a grumbling indistinct manner, indicating discontent or displeasure; to mutter.

To chew something gently with closed lips.

To utter with a low, inarticulate voice.

To chew or bite gently, as one without teeth.

To suppress, or utter imperfectly.