gainsay

gainsay \gayn-SAY; GAYN-say\, transitive verb:

1. To deny or dispute; to declare false or invalid.
2. To oppose; to contradict.

In our present, imperfectly postmodern world, where most information still takes the potentially embarrassing form of printed matter lurking in archives, liars still must position themselves so that the historical record may not easily gainsay them.
-- Thomas M. Disch, The Dreams Our Stuff Is Made Of

But, owing to government's cynical policy of inaction, suppression and hoping the problem would go away, there was nothing to gainsay it either.
-- Mary Riddell, "I don't mind about midsummer madness, but I'd rather not have it in my fridge or purring on the sofa", New Statesman, July 26, 1996

Gainsay comes from Middle English geinseien, from gein-, "against" (from Old English gegn-, gean-) + sayen, "to say," from Old English secgan.