suicide pact
noun [ C ] uk/ˈsuː.ɪ.saɪd ˌpækt/ us/ˈsuː.ɪ.saɪd ˌpækt/
（集体）自杀协定
an agreement between two or more people to kill themselves together at the same time
The leader of the religious sect and 30 of his followers killed themselves in a suicide pact last year. 去年那个宗教教派的领袖同30名追随者签署了自杀协定，集体自杀了。