ground alert

• n. 戒备状态；进入戒备状态之信号

例句

用作名词 (n.)

1. They have put the army on the alert.
   他们已使军队进入戒备状态。
2. These networks are on the alert for warning signs that show the weakening of rock layers that can precede an earthquake.
   这些网络始终处于戒备状态，搜索地震前岩石可能松动的警告迹象。