daydream

US /ˈdeɪ.driːm/
UK /ˈdeɪ.driːm/
1.

白日夢

a series of pleasant thoughts about something you would prefer to be doing or something you would like to achieve in the future:

:
He never paid attention in class and seemed to be in a permanent daydream.
1.

白日夢

to spend time thinking pleasant thoughts about something you would prefer to be doing or something you would like to achieve in the future:

:
Stop daydreaming and do some work!