indiscriminate, mass, wholesale
the indiscriminate slaughter of civilians

senseless, terrible | ritual

prevent, stop
We were helpless to stop the slaughter.

house (also ‘slaughterhouse’)

for ~
transporting live horses for slaughter

humanely
The animals are all humanely slaughtered.

ritually | illegally
elephants illegally slaughtered by poachers

for
Thousands of birds were slaughtered for their feathers.

brutally, cruelly
Hundreds of innocent civilians were cruelly slaughtered.