The Collaborative International Dictionary of English v.0.48:

Disaffirmance \Dis`af*firm"ance\, n.
   1. The act of disaffirming; denial; negation.
      [1913 Webster]

   2. (Law) Overthrow or annulment by the decision of a superior
      tribunal; as, disaffirmance of judgment.
      [1913 Webster]