expression
have a good time!; make the most of your time!
A polite, somewhat formal expression wishing someone a meaningful or enjoyable time. Often used in farewells, speeches, or written messages.
ご旅行中、有意義に過ごしてください。
Have a meaningful time during your trip.
残りの夏休みを有意義に過ごしてください。
Make the most of the rest of your summer vacation.
More casual and common; simply means 'enjoy yourself', without the nuance of 'meaningful' or 'productive'.
Similar polite wish, but focuses on having a good time rather than a meaningful one.
Phrase composed of 有意義 (meaningful) + に (adverbial particle) + 過ごす (to spend time) in て-form + ください (polite request). The components are standard modern Japanese.