警戒
❶warn;admonish
❷be on the alert against;guard against;keep a close watch on
采取~措施take precautionary measures /~部队outpost troops;vigilance corps;security force (or detachment)/~级别warning level/~哨outguard; picket guard/~水位warning line; warning water level/~线danger mark;security line;cordon/~状态state of alert