1. Indistinct enunciation
   "His mumbling made it difficult for the audience to understand his speech"
    
2. Ineffectual chewing (as if without teeth)
   "His mumbling of the food showed he needed dental work";
   - gumming

1. Talk indistinctly, usually in a low voice
   "He mumbled to himself while reading the document";
   - mutter, maunder, mussitate [archaic]
    
2. Grind with the gums; chew without teeth and with great difficulty
   "the old man had no teeth left and mumbled his food";
   - gum

Derived forms: mumblings

Type of: chew, chewing, diction, enunciation, manducate [archaic], manduction, masticate, mastication, mouth, speak, talk, utter, verbalise [Brit], verbalize

Encyclopedia: Mumbling