1. 汽笛;警报器
    A siren is a warning device which makes a long, loud noise. Most fire engines, ambulances, and police cars have sirens.

    e.g. It sounds like an air raid siren.
           那听起来像是空袭警报。

2. 妖艳而危险的女人;妖妇
    Some people refer to a woman as a siren when they think that she is attractive to men but dangerous in some way.

siren

    e.g. He depicts her as a siren who has drawn him to his ruin.
           他把她描述成是红颜祸水——就是她毁掉了自己。
    e.g. ...the voluptuous siren with a husky voice.
           这个声音沙哑、性感迷人的妖女

3. 诱人的东西;诱惑
    A siren call or siren song is the appeal that something has although it is harmful or dangerous.

    e.g. Unable to resist the siren call of the cards, he withdrew their savings and headed for Las Vegas...
           他无法抵挡赌牌的诱惑，便提取了他们的存款前往拉斯韦加斯。
    e.g. He said the United States was not willing to engage in a search for partial solutions — to succumb, as he put it, to a siren song.
           他说美国不愿意参与仅仅解决部分问题的方案的探索——按照他的说法，这种做法就是向诱惑低头。