To gainsay is to declare false or to contradict. It’s a transitive verb, meaning it has to act upon something. So you can’t just say “I gainsay,” period; you have to gainsay something. And what’s gainsaid is not the person you disagree with but the statement you wish to contradict. For instance, if you disagree with our definition of gainsay, you don’t gainsay us; you gainsay our definition.
Though gainsay has a certain appeal, it can have an archaic ring outside legal contexts, and it often bears replacement with alternatives such as dispute and contradict. There’s nothing incorrect about it, though, and it does appear occasionally even in mainstream writing from this century.
The word has origins in Old English. The first syllable, gain, is etymologically related to against (and is unrelated to our modern sense of gain), so we can think of gainsay as a sort of contraction of say against.
Lords, knights, and gentlemen, what I should say, / My tears gainsay; for every word I speak, / Ye see, I drink the water of mine eyes. [King Henry VI, William Shakespeare]
None could predict his word, and a whole congress could not gainsay it when it was spoken. [“The Fortune of the Republic,” Ralph Waldo Emerson]
It cannot be gainsaid that Prosperity has been the feature of the country during the administration of Sir Robert Bond. [Evening Telegram (1908)]
There is no gainsaying the fact that most of us live too strenuously, hurry too much to no purpose, are too nearly “full of sound and fury, signifying nothing.” [Spokane Daily Chronicle (1905)]
Without gainsaying that Dharun Ravi was guilty of a hate crime, the prosecution never proved that he hated gays. [Technorati]
But Western culpability and hypocrisy cannot be used to gainsay another unarguable fact – that the Rajapaksa regime too is innocent neither of hypocrisy nor of crimes. [Sunday Leader]
China’s development reflects decisions taken at the centre and the point may have arrived where the benefits of liberalisation cannot be gainsaid. [Gulf Daily News]