ジェノサイド。
「大量虐殺」と訳されることが多い。(ただし、その訳語では語義を厳密に伝えられない場合がある。)
国際法的な定義は以下のとおり。なお、国際法上の定訳は「集団殺害(罪)」。
Convention on the Prevention and Punishment of the Crime of Genocide
http://www.ohchr.org/english/law/genocide.htm
Article II
In the present Convention, genocide means any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such:
( a ) Killing members of the group;
( b ) Causing serious bodily or mental harm to members of the group;
( c ) Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part;
( d ) Imposing measures intended to prevent births within the group;
( e ) Forcibly transferring children of the group to another group.
ミネソタ大学人権センターによる和訳
http://www1.umn.edu/humanrts/japanese/Jx1cppcg.htm
ジェノサイド条約 - Wikipedia日本語版
国際刑事裁判所規程第6条も参照のこと。
http://www.preventgenocide.org/law/icc/statute/part-a.htm#2
The Penguin Dictionary of Sociology (Dictionary, Penguin)