[1] : The Collaborative International Dictionary of English v.0.48

undeniably \un`deni"ably\, adv.
   in an undeniable manner.
   1913 webster

[2] : WordNet (r) 2.0

undeniably
     adv : to an undeniable degree or in an undeniable manner; "she is
           undeniably the most gifted student in the class"

[3] : Moby Thesaurus II by Grady Ward, 1.0

40 moby thesaurus words for "undeniably":
   actually, admittedly, assuredly, beyond doubt, beyond question,
   certainly, clearly, decidedly, demonstrably, doubtless,
   doubtlessly, for a certainty, for real, in all conscience,
   incontestably, indeed, indisputably, indubitably, irrefragably,
   irrefutably, manifestly, no doubt, noticeably, observably,
   obviously, out of question, patently, positively, quite, really,
   sensibly, seriously, truly, unambiguously, undoubtedly,
   unmistakably, unquestionably, verily, visibly, without doubt

Undeniably >> U Words
Undeniably, definition of term: Undeniably
undeniably_pag1.html