Nouns

(n)refutation, defense, defencethe speech act of answering an attack on your assertions“his refutation of the charges was short and persuasive”, “in defense he said the other man started it”
(n)disproof, falsification, refutationany evidence that helps to establish the falsity of something
(n)falsification, falsifying, disproof, refutation, refutalthe act of determining that something is false