What does Ezekiel 21:14 mean?

So, son of man, prophesy and clap your hands. Let the sword strike again and again, three times. It’s the sword for those to be killed, a sword for a great slaughter, closing in on them from every side. Ezekiel 21:14 - Modern Text Bible

(Ezekiel is to act out the coming violence, showing that the destruction will be relentless and widespread.)