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 utter indistinctly by lowering the voice or partially closing the mouth: mumbled an insincere apology.
- To chew slowly or ineffectively without or as if without teeth.
- To speak words indistinctly, as by lowering the voice or partially closing the mouth.
- To chew food slowly or ineffectively, as if with the gums.
- A low indistinct sound or utterance.