worried or frightened by something

I was a bit alarmed at/by how much weight she'd lost. 看到她瘦了那么多，我有点儿担心了。

[ + to infinitive ] I was alarmed to hear that she was coming. 听到她要来，我慌了神。

[ + that ] I'm rather alarmed that we haven't heard anything. 我们什么消息也没有听到，我非常担忧。

An alarmed vehicle or place has an alarm in it that, when active, will make a loud noise if anyone enters or touches it.

Warning: this building is alarmed. 警告：本楼装有警报系统。