on the alert
1. 警戒着; 随时准备着
They have put the army on the alert.
他们已使军队进入戒备状态。
习惯用语air alert1.空袭警报; 空中待机(飞机起飞, 在空中待命)air-raid alert1.空袭警报be on the alert1.注意; 提防; 警戒blue alert1.(预备警报后的)空袭警报; 台风警报put on the alert1.(军队)处于戒备状态red alert1.紧急警报; 紧急戒备white alert1.解除警报alert to do1.留心做alert ...to the fact that1.提醒...注意如下事实yellow alert1.预备警报特殊用法active alert1.战斗警报battle alert1.战斗警报ground alert1.地面待战[值班]; 地面待战信号[飞机]long-duration alert1.长期待战[戒备]malfunction alert1.故障报警器alert by radar1.雷达警戒