He spilled red wine on the host's clothes at the dinner party, committing a serious gaffe.

gaffe 是名词，来自法语，指"社交场合中因言行不当而造成的尴尬或失礼"，通常是无心之失但显得很不得体。在英语中专指这种社交礼仪上的失误，比普通用词"mistake"更具体。