noun
mass killing; genocide
Refers to the killing of a large number of people as a group, often in contexts of war crimes or systematic violence. 集団殺害 is a direct compound; ジェノサイド is also common in Japanese.
その国では集団殺害が行われたと報告されている。
It is reported that mass killings were carried out in that country.
Under international law, genocide is considered a serious crime.