1. 警觉的;警惕的
    Someone who is watchful notices everything that is happening.

    e.g. The best thing is to be watchful and see the family doctor for any change in your normal health...
           最佳的做法是保持警惕，一旦你的身体状况有任何变化就立即去看家庭医生。
    e.g. He looked tall and powerful and, with his dark, watchful face, a little threatening.
           他看上去又高又壮，面色黝黑，满脸警觉，真叫人有点害怕。

2. 在(某人)的警觉目光下；在…的监视下
    If you do something under the watchful eye of someone who has authority over you, they watch you carefully to make sure there are no problems.

watchful什么意思

    e.g. There were demonstrations in the streets today, under the watchful eye of police...
           今天，在警方的监视下大街上进行了游行。
    e.g. Children swim at the pool, under the watchful eye of lifeguards.
           孩子们在救生员的监护下在水池里游泳。

3. 看护;提防
    If you keep a watchful eye on someone or something, you watch carefully to make sure there are no problems.

u0039u0031u0031u67E5u8BE2u00B7u82F1u8BEDu5355u8BCD

    e.g. Keep a watchful eye on babies and toddlers.
           要看好婴儿和刚会走路的孩子。