gainsay

/ˌgān-ˈsā/

Middle English yein seyen, gein-seyen "to speak in opposition to, deny," from yein-, gein- "away, back, against, in opposition to" (going back to Old English gēan- "in opposition to," or marking returning or reciprocal action, going back to Germanic *gagna-) + seyen "to "

verb

  1. to declare to be untrue or invalid

  2. contradict, oppose

deny gainsay contradict contravene mean to refuse to accept as true or valid. deny implies a firm refusal to accept as true, to grant or concede, or to acknowledge the existence or claims of. gainsay implies disputing the truth of what another has said.