1(of an occurrence) become as though never having happened; be reversed.
（已发生事）似乎从未发生
things had happened that could never unhappen
覆水难收。
Example sentencesExamples
But her blissful countenance made every bad thing unhappen.
The truth of the proposition is based on the fact that there has been a case of my going to Athens, and - whatever happens from now on - this cannot unhappen.
To paraphrase P.J. O'Rourke, unapproved interactions unhappen in Pyongyang.
1.1with objectCause (something) not to have happened.
you can't unhappen it just by saying we won't speak of it again
Example sentencesExamples
I went to see a lovely Irish padre, who said: ‘If you can't unhappen it, don't worry about it.’
Definition of unhappen in US English:
unhappen
verbˌənˈhapən
[no object]
1(of an occurrence) become as though never having happened; be reversed.
（已发生事）似乎从未发生
things had happened that could never unhappen
覆水难收。
Example sentencesExamples
To paraphrase P.J. O'Rourke, unapproved interactions unhappen in Pyongyang.
The truth of the proposition is based on the fact that there has been a case of my going to Athens, and - whatever happens from now on - this cannot unhappen.
But her blissful countenance made every bad thing unhappen.
1.1with objectCause (something) not to have happened.
you can't unhappen it just by saying we won't speak of it again
Example sentencesExamples
I went to see a lovely Irish padre, who said: ‘If you can't unhappen it, don't worry about it.’