Webster's Revised Unabridged Dictionary · 1913

Gainsay

Gainsay (? o?; 277) , transitive verb

[Old English geinseien, ageinseien. See Again, and Say to utter.]

To contradict; to deny; to controvert; to dispute; to forbid.
I will give you a mouth and wisdom which all your adversaries shall not be able to gainsay nor resist. — Luke xxi. 15
The just gods gainsay That any drop thou borrow'dst from thy mother, My sacred aunt, should by my mortal sword Be drained. — Shakespeare