Definition of massacre:
(n) :
the intentional killing of a considerable number of human beings, under circumstances of atrocity or cruelty, or contrary to the usages of civilized people; murder
(v) :
to kill in considerable numbers where much resistance can not be made; to kill with indiscriminate violence, without necessity, and contrary to the usages of nations; to butcher; to slaughter - limited to the killing of human beings