This was such a great breach of etiquette, he hardly knew what to do.

这是一起规矩的严重违反，他几乎不知所措了。

《柯林斯英汉双解大词典》

Had we consulted the website of the Emily Post Institute, this embarrassing breach of etiquette could have been avoided.

如果我们咨询过艾米莉·波斯特学院的网站，这个尴尬的违反礼仪就可以避免了。

youdao

The university itself was loathe to see a breach of etiquette.

至于剑桥大学校方，也绝不愿见到失礼事件。

youdao

This comment on a neighbour's internal politics was a breach of South-East Asian etiquette.

ECONOMIST: Lee Kuan Yew: an apology

The firm started a blog on social media etiquette in early 2009 when few others were willing to breach the boundary of the company intranet to focus on connecting with employees and customers.

FORBES: How to Design a Social Media Policy