The phrase "be irrefutable" means to be impossible to refute or argue against. Some synonyms for this phrase include being undeniable, indisputable, incontestable, and unassailable. These words convey the idea that there is no room for doubt or debate on the matter at hand. Other synonyms for "be irrefutable" include being certain, unquestionable, and absolute. When describing evidence or arguments as irrefutable, you could also use terms such as convincing, compelling, or persuasive. Overall, the concept of being irrefutable suggests that something is so clear and undeniable that it cannot be disputed or contradicted in any way.