mumble
verb /ˈmʌmbl/
  /ˈmʌmbl/
[intransitive, transitive]Verb Forms
| present simple I / you / we / they mumble |  /ˈmʌmbl/  /ˈmʌmbl/ | 
| he / she / it mumbles |  /ˈmʌmblz/  /ˈmʌmblz/ | 
| past simple mumbled |  /ˈmʌmbld/  /ˈmʌmbld/ | 
| past participle mumbled |  /ˈmʌmbld/  /ˈmʌmbld/ | 
| -ing form mumbling |  /ˈmʌmblɪŋ/  /ˈmʌmblɪŋ/ | 
- to speak or say something in a quiet voice in a way that is not clear synonym mutter- mumble (to somebody/yourself) I could hear him mumbling to himself.
- mumble something (to somebody/yourself) She mumbled an apology and left.
- + speech ‘Sorry,’ she mumbled.
- mumble that… She mumbled that she was sorry.
- mumble about something I couldn't understand what he was mumbling about.
 Extra Examples- George mumbled incoherently to himself.
- She mumbled something into her pillow.
 Oxford Collocations Dictionaryadverb- incoherently
- quietly
- softly
- …
 - about
- into
- to
- …
 Word OriginMiddle English: frequentative of mum (adjective).