The Collaborative International Dictionary
Disaffirm
Disaffirm \Dis`af*firm"\, v. t.
To assert the contrary of; to contradict; to deny; -- said of that which has been asserted.
(Law) To refuse to confirm; to annul, as a judicial decision, by a contrary judgment of a superior tribunal.
Wiktionary
disaffirm
vb. To deny, contradict or repudiate