The dynamic I match it to is “being mean for its own sake, to a specific individual, over an extended period of time, in an environment where they can’t get away from their tormentor(s).” The social equivalent of a cat playing with a mouse it’s caught.
N=1 for this interpretation, and it may not be quite necessary or sufficient even by my own lights.
Edit: A more succinct definition might be: “Bullying: persistent, targeted cruelty.”
This bears repeating. I’d add another distinction: If you’re talking about policy, you’re probably OK; if you’re talking about people, you’re probably not.
(also, on a purely selfish note, the contemporary political shitstorm has taken over every other venue I communicate in and I really would rather not see it here)