Source : Webster's Revised Unabridged Dictionary (1913)

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

   Syn: Incontrovertible; unanswerable; indisputable;
        unquestionable; incontestable; indubitable; undeniable;
        irrefutable.