1. 违抗;反抗;不服从
    If you defy someone or something that is trying to make you behave in a particular way, you refuse to obey them and behave in that way.

    e.g. This was the first (and last) time that I dared to defy my mother...
           这是我第一次(也是最后一次)胆敢反抗我的母亲。
    e.g. Nearly eleven-thousand people have been arrested for defying the ban on street trading.
           将近有1.1万人因为违抗禁止在街上摆摊交易的禁令而被捕。

2. 挑战;激;认为…不敢(或无法)（做）
    If you defy someone to do something, you challenge them to do it when you think that they will be unable to do it or too frightened to do it.

    e.g. I defy you to come up with one major accomplishment of the current Prime Minister...
           我敢说你讲不出现任首相的哪怕一项重大成就。
    e.g. He looked at me as if he was defying me to argue.
           他看着我，仿佛在激我与他争论。

3. 无法，难以(描述或理解)
    If something defies description or understanding, it is so strange, extreme, or surprising that it is almost impossible to understand or explain.

    e.g. When the flowers open in spring they fill the night air with a fragrance that defies description...
           春天鲜花开放时，夜里的空气中会弥漫一种难以名状的香气。
    e.g. It's a devastating and barbaric act that defies all comprehension.
           这种行为野蛮凶残、令人震惊，简直是不可理喻。

4. 看上去比实际年轻
    If you say that someone defies their age, or defies the years, you mean that their appearance or behaviour suggests that they are younger than they really are.

defy在线翻译

    e.g. The singer continues to defy her age by wearing the scantiest of outfits.
           那名女歌手依旧穿着非常暴露的服装，完全不似她这把岁数。