s carefully observant or attentive; on the lookout for possible danger
a. 警觉的, 警戒的, 警惕的
[法] 警醒的, 警戒的, 注意的
1. The security guard remained vigilant throughout the night.
保安整夜保持警惕。
2. It's important to be vigilant when driving in bad weather.
在恶劣天气下开车时保持警惕是很重要的。
3. She was vigilant about checking her emails for any important updates.
她时刻注意查看邮件，以获取任何重要更新。