[syn: decidedly, unquestionably, emphatically, definitely, in spades, by all odds]
The Collaborative International Dictionary of English v.0.48:
Unquestionable \Un*ques"tion*a*ble\, a.
   1. Not questionable; as, an unquestionable title.
      [1913 Webster]
   2. Not inviting questions or conversation. [R.] --Shak.
      [1913 Webster] -- Un*ques"tion*a*bly, adv.
      [1913 Webster]
WordNet (r) 3.0 (2006):
unquestionably
    adv 1: without question; "Fred Winter is unquestionably the
           jockey to follow"; "they hired unimpeachably first-rate
           faculty members" [syn: unquestionably, unimpeachably]
    2: without question and beyond doubt; "it was decidedly too
       expensive"; "she told him off in spades"; "by all odds they
       should win" [syn: decidedly, unquestionably,
       emphatically, definitely, in spades, by all odds]