refutation

(noun) the speech act of answering an attack on your assertions. Synonyms: defense, defence. Examples: "His refutation of the charges was short and persuasive." "In defense he said the other man started it."

(noun) any evidence that helps to establish the falsity of something. Synonyms: disproof, falsification.

(noun) the act of determining that something is false. Synonyms: falsification, falsifying, disproof, refutal.