That mumbles (in various senses); consisting of mumbles or mumbling. Also figurative.

figurative. That does something clumsily or awkwardly; also, hesitating in speech, mumbling.

That mutters; speaking indistinctly and in a low tone. Also figurative.

That causes a person to speak indistinctly.

That mutters or murmurs; that speaks in an undertone.

Characterized by mumbling; inclined to mumble.