The Collaborative International Dictionary of English v.0.48:
Disaffirmation \Dis*af`fir*ma"tion\, n. The act of disaffirming; negation; refutation. [1913 Webster]WordNet (r) 3.0 (2006):
disaffirmation n 1: the act of asserting that something alleged is not true [syn: denial, disaffirmation]