Definition of "gainsay"
gainsay
verb
third-person singular simple present gainsays, present participle gainsaying, simple past and past participle gainsaid
(transitive, formal) To say something in contradiction to.
Quotations
[…] vve are able with playne demonſtration to proue, and vvith reaſon to perſvvade that in tymes paſt our fayth vvas alike, that then vve preached thinges correſpondent vnto the forme of faith already publiſhed of vs, ſo that none in this behalfe can repyne or gayneſay vs.
1577, Socrates Scholasticus [i.e., Socrates of Constantinople], “Constantinus the Emperour Summoneth the Nicene Councell, it was Held at Nicæa a Citie of Bythnia for the Debatinge of the Controuersie about the Feast of Easter, and the Rootinge out of the Heresie of Arius”, in Eusebius Pamphilus, Socrates Scholasticus, Evagrius Scholasticus, Dorotheus, translated by Meredith Hanmer, The Avncient Ecclesiasticall Histories of the First Six Hundred Yeares after Christ, Wrytten in the Greeke Tongue by Three Learned Historiographers, Eusebius, Socrates, and Euagrius. [...], book I (The First Booke of the Ecclesiasticall Historye of Socrates Scholasticvs), imprinted at London: By Thomas Vautroullier dwelling in the Blackefriers by Ludgate, page 225
Know then that in the time of the Great Rebellion (the history of which by the learned Lord Clarendon I most earnestly commend to your attention) this Manor of Baskerville was held by Hugo of that name, nor can it be gainsaid that he was a most wild, profane, and godless man.
1902, Arthur Conan Doyle, The Hound of the Baskervilles
And there was something childlike about Griffith, too, even in his Matlock days, as a deceptively sharp 'simple country lawyer,' a big-kid boyishness that did not mask his intelligence or gainsay his authority.
2012 July 7, “Griffith acted, and lived, by Golden Rule”, in The Post and Courier, Charleston: Evening Post Publishing, page 5, Features