slaughter: the butchering of an animal, and the cutting down of people pictured as exactly that
This is the butcher's word. Its home is the ordinary work of killing an animal and dressing it so that a meal can be cooked, which is what Joseph orders when his brothers arrive for lunch and what Wisdom does before she lays her table. Nothing in it points to an altar. The killing is skilled, deliberate work done with a knife so that somebody can eat.
The prophets take that everyday picture and turn it on people. When Isaiah says the nations are handed over to slaughter, or Jeremiah says the finest young men of Moab have gone down to it, the horror lies in the comparison: human beings are being handled the way a butcher handles livestock, unresisting and already counted out. Ezekiel builds a whole poem around it, a sword drawn, sharpened and polished for this one purpose. The image can also run the other way and describe the victim rather than the killer, as with the sheep that goes to the knife and does not open its mouth.
Because animals are killed at the altar too, this word runs close to the language of sacrifice (זֶבַח) without ever becoming it. Isaiah 34:6 sets the two side by side, a sacrifice in Bozrah and a great slaughter in the land of Edom, and the line works only because they are different words: one names an offering made to God, the other names butchery. Where a text wants the plain fact of people being killed with no such picture at all, it reaches for a different word (הֶרֶג).