形容词

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

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.

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.