Noah Webster's New International Dictionary of the English Language

1. (v.) 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.

2. (v.) To chew something gently with closed lips.

3. (v. t.) To utter with a low, inarticulate voice.

4. (v. t.) To chew or bite gently, as one without teeth.

5. (v. t.) To suppress, or utter imperfectly.