He opened his mouth to speak but mumbled and hesitated.
Tips
history
嗫 is not used alone; it survives only in the literary binome 嗫嚅 - moving the lips as if to speak but not getting words out, i.e. mumbling hesitantly. It is the mouth radical 口 plus the phonetic 聂, which also feeds 蹑 and 镊.
register
Literary and bound only; modern speech says 支支吾吾 for hesitant mumbling.
聂 supplies the sound niè. It is built from ears and carries a faint whispering flavour, fitting for halting half-spoken words. The same phonetic appears in 镊 and 蹑.
