a. [ F. irréfragable, L. irrefragabilis. See Refragable. ] Not refragable; not to be gainsaid or denied; not to be refuted or overthrown; irrefutable; unanswerable; incontestable; undeniable; as, an irrefragable argument; irrefragable evidence. -- Ir*ref"ra*ga*ble*ness, n. -- Ir*ref"ra*ga*bly, adv.