black tie event意思是要求穿正规晚礼服的正式社交活动；需穿正装出席的场合。

【例句】
The awards ceremony will be a black tie event, so I’ll have to buy a smart suit. My wife is going to wear her purple ball gown.
颁奖典礼需穿正装，因此我得买套时髦的衣服。妻子打算穿那件紫色舞袍。

Some of the company parties are black-tie events.
有些公司的年终庆祝派对是要求穿正规晚礼服的正式社交活动。