refutation

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The act of refuting.
• noun Something, such as an argument, that refutes someone or something.

from The Century Dictionary.

• noun The act of refuting or disproving; the overthrowing of an argument, opinion, testimony, doctrine, or theory by argument or countervailing proof; confutation; disproof. Refutation is distinguished as direct or ostensive, indirect or apagogical, a priori or a posteriori, according to the kind of reasoning employed.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act or process of refuting or disproving, or the state of being refuted; proof of falsehood or error; the overthrowing of an argument, opinion, testimony, doctrine, or theory, by argument or countervailing proof.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An act of refuting or disproving; the overthrowing of an argument, opinion, testimony, doctrine or theory by argument or countervailing proof; confutation; disproof; evidence of falseness.
• noun A vocal answer to an attack on one's assertions

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the act of determining that something is false
• noun the speech act of answering an attack on your assertions
• noun any evidence that helps to establish the falsity of something