The inns are informal and dress-up clothes are not required for dinner.

小旅馆是非正式场所，所以就餐不需要考究的衣服。

《柯林斯英汉双解大词典》

I think they're excused to dress up in fancy clothes.

我想他们有理由打扮得漂漂亮亮的。

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Many days, her home is strewn with dress-up clothes, art supplies and other artifacts from playtime with her two small children, Benjamin, 6, and Laura, 3.

许多天来，她和两个孩子：6岁的本杰明和3岁的劳拉享受着娱乐时间，因而她家到处散落着戏剧服装，化妆工具及其他物品。

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putting it with regular clothes to make it dressed down. But you can dress it up with heels.

跟日常的衣服搭在一起，显得随意一点。不过，你可以搭双高跟鞋。

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but also I think they're excused to dress up in fancy clothes

但是，我觉得他们是要借此机会盛装打扮一下，

英国皇家赛马会 - SpeakingMax英语口语达人

Designed by fashion icon Betsey Johnson, the pink paradise is complete with pink-and-white striped wallpaper, a table set for a fancy tea party and a closet stuffed with dress-up clothes.

FORBES: Hotel Suites With One-Of-A-Kind Themes

Other theatrical adventures involve entering a wardrobe to find a secret room where an actor will dress you up in odd clothes, entering a 15-minute relationship or taking the chance to interrogate characters taken from the morning's newspapers about their role in the story.

BBC: A theatre play - all to yourself