CsLewis The practice of dismissing a person’s arguments not on the basis of the argument(s) themselves, but by first assuming as a given that the person is wrong and then inventing some explanation after the fact. Similar to ad hominem, but instead of “you are wrong because you are a bad person”, it’s more “your badness as a person is why you are wrong”.
(The full essay on the topic can be read at https://matiane.wordpress.com/2019/01/15/bulverism-by-c-s-lewis/ )