ADJ-GRADED 警惕的;警觉的;警戒的 Someone who is vigilant gives careful attention to a particular problem or situation and concentrates on noticing any danger or trouble that there might be. 警惕的;警觉的;警戒的
He warned the public to be vigilant and report anything suspicious.
他警告公众要提高警惕,遇到任何可疑情况都要报告。
All but one of these letter bombs had been intercepted by vigilant post office staff.