Is “Mumbles” a Scrabble word?
Yes
MUMBLES
Valid in at least one Scrabble dictionary
Valid in these dictionaries
SOWPODS / CSW
Scrabble UK & International
TWL / NWL
Scrabble North America
Large English Dictionary
General English word list
Meaning of Mumbles
noun
1.A quiet or unintelligible vocalization; a low tone of voice.
“All I could hear was a mumble from the next room.”