If you are discreet, you are polite and careful in what you do or say, because you want to avoid embarrassing or offending someone.
They were gossipy and not always discreet.
他们爱说闲话,而且不总是言语谨慎。
If you are discreet about something you are doing, you do not tell other people about it, in order to avoid being embarrassed or to gain an advantage.
We were very discreet about the romance.
我们对这一段罗曼史守口如瓶。
If you describe something as discreet, you approve of it because it is small in size or degree, or not easily noticed.
She is wearing a noticeably stylish, feminine dress, plus discreet jewellery.
她穿着一条非常时髦、有女人味的连衣裙,配以小巧的首饰。