This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

v. To establish the falsity of a claim or belief; to show or to tend to show that a theory or hypothesis is not valid.

"She asked me if this sounded like the woman Susy would bring along, and I told her I was not at liberty to confirm or disconfirm this possibility."

confirm   

disconfirming   

disconfirmation