Source : Webster's Revised Unabridged Dictionary (1913)

Indubitable \In*du"bi*ta*ble\, a. [L. indubitabilis: cf. F.
   indubitable. See {In-} not, and {Dubitable}.]
   Not dubitable or doubtful; too evident to admit of doubt;
   unquestionable; evident; apparently certain; as, an
   indubitable conclusion. -- n. That which is indubitable.

   Syn: Unquestionable; evident; incontrovertible;
        incontestable; undeniable; irrefragable.

Source : WordNet®

indubitable
     adj : too obvious to be doubted [syn: {beyond doubt(p)}]