a particular but not obvious characteristic that a piece of writing or speech, an event, or a situation has

I thought her speech had slightly sinister undertones. 我认为她的话里有点儿不祥的意味。

It was a comedy act with an undertone of cruelty. 这是一个有点儿残忍的喜剧节目。

a colour, smell, flavour, etc. that is part of something but not the most obvious part

The elephant's pale grey skin carries undertones of violet. 大象的皮肤在浅灰色中带着一丝紫色。

The gin has a unique crisp flavour that is very well-balanced with light, sweet undertones. 这种杜松子酒具有独特的清新风味，与其清甜的余味平衡得非常好。

in a very quiet voice

Freddie muttered something to me in an undertone. 弗雷迪轻声向我嘀咕了些什么。

They spoke in undertones in order not to startle the animal. 为了不惊动动物，他们轻声地说话。