1. There is an undertone of regret in what he said.
    他的话中带有悔意。

2. undertone在线翻译

2. They are talking in undertones.
    他们在低声说话。

1. undertone

1. 底色：大部份应用的钛白粉品级在颜色上不会有明显的变化,然而,下列因素会导致低劣的颜色: 污染(contamination) 钛白粉和树脂或添加剂(additives)的反应 热安定性(heat stability)失效 颜色(color)和底色(undertone)有时令人混淆不清.

2. 低调：然而英国电影取比较阴沉、低调(undertone)的处理方式,来看这段相当凄美的爱情故事,美的如影子那麼朦朧,那麼捉摸不定. 所以本来有两个孩子改为独子,本来还可两度出国度蜜月也改成单独一次. 虽一再重復「阅读使人不致孤独,进而爱才能解决孤单」,

3. 弦外之音：accent 重音 | tone-overtone言外之意 | undertone弦外之音

4. 低音：undertax 课税太低 | undertone 低音 | undertook 承担

1. 低声；悄声
    If you say something in an undertone, you say it very quietly.

    e.g. ''What d''you think?'' she asked in an undertone...
           “你觉得怎么样？”她小声地问道。
    e.g. Well-dressed clients were talking in polite undertones as they ate.
           衣着光鲜的顾客们边吃边斯文地低声聊着天。

2. 言下之意；寓意
    If something has undertones of a particular kind, it suggests ideas or attitudes of this kind without expressing them directly.

    e.g. The sobbing voice had an undertone of anger.
           啜泣声中隐隐透着愤怒。
    e.g. ...a witty, racy story with surprisingly serious undertones.
           诙谐却寓意深刻的荤段子

1. a pale or subdued color

    Synonym: tinge

2. a subdued emotional quality underlying an utterance
    implicit meaning

    Synonym: undercurrent

3. a quiet or hushed tone of voice

    e.g. spoke in undertones