a device that makes a long loud sound as a signal or warning 汽笛；警报器；警笛
an air-raid siren
空袭警报器
A police car raced past with its siren wailing.
一辆警车鸣着警报器飞驰而过。
(in ancient Greek stories) any of a group of sea creatures that were part woman and part bird, or part woman and part fish, whose beautiful singing made sailors sail towards them into rocks or dangerous waters 塞壬（古希腊神话中半人半鸟或半人半鱼的女海妖，以美妙歌声诱使水手驶向礁石或进入危险水域）