CEDICT
alarm; warning; alert
Wiktionary
对可能或即将来临的危急事件所作的警戒报讯。
重編國語辭典
对可能或即将来临的危急事件所作的警戒信号
維基詞典
The fire alarm rang.
Source: Tatoeba
The tsunami alert was cancelled.
This was a warning: the floods were coming.
This startled me.