/ ˈrevəri; NAmE / noun
[ C , U ] ( formal ) a state of thinking about pleasant things, almost as though you are dreaming
SYN daydream :
She was jolted out of her reverie as the door opened.
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WORD ORIGIN
early 17th cent.: from obsolete French resverie , from Old French reverie rejoicing, revelry, from rever be delirious, of unknown ultimate origin.