a person who often thinks about doing something else or being somewhere else, instead of paying attention to what is happening where they are now

I'm still a bit of a daydreamer. 我仍然是个爱做一点白日梦的人。

He was a daydreamer who grew sullen when faced with textbooks. 他是一个做白日梦的人，一面对教科书就变得闷闷不乐。