Which term means to declare false or deny something?

The term that means to declare false or deny something is "gainsay." This word specifically refers to the act of denying or contradicting a statement or assertion. It is often used in contexts where one party is openly opposing or declaring something to be untrue.

In contrast, "contradict" also relates to denying or opposing a statement, but it typically applies to situations where one assertion directly opposes another. "Refute" goes a step further, as it implies that someone not only denies a claim but also provides evidence or argument to prove the claim false. "Dispute" indicates a disagreement over an issue but doesn't necessarily imply a direct denial—it's more about contesting or arguing various aspects of the topic.

In summary, "gainsay" directly captures the essence of declaring something false or denying it, making it the most accurate choice in this context.