"Irrefragably" is a word that means unequivocally or indisputably. It can be challenging to find synonyms that perfectly encapsulate the same meaning, but some alternatives to "irrefragably" include "undeniably," "incontestably," "unquestionably," "indubitably," and "unarguably." These words all convey the idea of something being so convincing or evident that it cannot be disputed or called into question. Other possible synonyms might include "undeniable," "surely," "certainly," "absolutely," or "positively." These words can be helpful for writers or speakers who want to emphasize the strength of their argument and present something as being beyond doubt or controversy.