I'm not sure if it's strictly defined. the way I see it used is to describe an (online) trend of "cancelling" somebody for something bad that they have done. the idea is that when somebody is cancelled, they should no longer be treated positively, for example losing their celebrity status.

it's a cute project but there's a reason next to nobody uses their software (because it all sucks)

their whole approach to technology is so gross anyway, I'm not surprised these pretentious pricks are nazis tbh