mutter

murmur, mutter, whisper

名词 mutter:

1. a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech
   同义词：muttering, murmur, murmuring, murmuration, mussitation
2. a complaint uttered in a low and indistinct tone
   同义词：grumble, grumbling, murmur, murmuring, muttering

动词 mutter:

1. talk indistinctly; usually in a low voice
   同义词：mumble, maunder, mussitate
2. make complaining remarks or noises under one's breath
   同义词：murmur, grumble, croak, gnarl

1. She kept on muttering to herself.
   她老是一个人嘀嘀咕咕。
2. Actors often mutter to themselves when rehearsing their lines.
   演员背台词的时候经常自己嘀嘀咕咕。

mut.ter

v.（动词）
mut.tered,mut.ter.ing,mut.ters
v.intr.（不及物动词）
To speak indistinctly in low tones.
咕哝：小声而含糊不清地说
To complain or grumble morosely.
阴郁的抱怨或者嘟哝
v.tr.（及物动词）
To utter or say in low, indistinct tones.
嘀咕：用小声的、不清楚的声音说话
n.（名词）
A low grumble or indistinct utterance.
咕哝：低声地嘟哝或者不清楚地说话

来源：
Middle English muttren
中古英语 muttren
possibly from Latin muttore
可能源自 拉丁语 muttore

【引伸】
mut.terer
n.（名词）