We don't have synonyms for mumblecore yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are dumbledore.
(n) :
(film) An American independent film movement or subgenre of the early twenty-first century, characterised by low-budget production, focus on personal relationships between twentysomethings, improvised scripts, and non-professional actors.
(n) :
(film) An American independent film movement or subgenre of the early twenty-first century, characterised by low-budget production, focus on personal relationships between twentysomethings, improvised scripts, and non-professional actors.