define mumble
verb. The definition of a mumble is something spoken in a low voice. An example of a mumble is how a shy child responds to a question. To mumble is to speak in a low voice that is often difficult to understand.An example of mumble is to answer a question in a low voice or without clearly sounding out the words.he definition of a mumble is something spoken in a low voice. An example of a mumble is how a shy child responds to a question. To mumble is to speak in a low voice that is often difficult to understand.