To cancel someone was really popular for a couple years starting just after covid. There's probably a better definition somewhere, but basically it is when a collective of like-minded people decide to publicly shame a person until they are too embarrassed to have an online presence, or even worse, until companies are pressured to not employ the person. It was like unofficial unions against someone existing. It stopped after enough people were cancelled that they were no longer powerless together. Then people who hate others had to evolve into different ways to be disrespectful because this method stopped working, which is why you don't see cancelling anymore