Slaughter refers to the killing of large numbers of animals or people. When cattle are old enough, they're sent to slaughter and their meat is processed and shipped to stores.
The noun slaughter was first used in the 1300s and comes from the Old Norse word slahtr, which also described the mass killing of animals or people. A verb form came along later, in the 1530s. You might hear slaughter used to describe the killing of large numbers of people in a war, a genocide, or a massacre. It also can be used figuratively to describe a crushing defeat, like the slaughter of your basketball team by your bitter rivals.