From Longman Dictionary of Contemporary Englishsuicide pactˈsuicide ˌpact noun [countable] KILLan arrangement between two or more people to kill themselves at the same time
Examples from the Corpus
suicide pact• Lowestoft is a town twinned with nowhere, although it is considering a suicide pact with Basildon.• Desperate and afraid, they formed a suicide pact.• So they joined in a suicide pact which would rid them for ever of parental domination.• Detectives are investigating whether it was an accident, a murder or a suicide pact.• At the moment they don't know whether this was an accident, a murder or a suicide pact. 