mumble

to speak in a low voice, making it hard to hear

to speak in a gentle, low voice

to speak unclearly out of anger

to speak in a way that is unclear and difficult to understand

to speak unclearly while expressing deep disappointment or resentment

to speak unclearly and rapidly

to say something unclearly in a sarcastic tone

to speak unclearly due to being tired

to speak unclearly in the direction of someone or to oneself

to speak unclearly with one's voice directed into an object, muffling the sound

to speak unclearly regarding a particular topic