DuckCorp Dico

Found one definition

1.                 From WordNet (r) 3.0 (2006):
                   
   
   
                   
                     
   mumble
       n 1: a soft indistinct utterance
       v 1: talk indistinctly; usually in a low voice [syn: mumble,
            mutter, maunder, mussitate]
       2: grind with the gums; chew without teeth and with great
          difficulty; "the old man had no teeth left and mumbled his
          food" [syn: mumble, gum]