The Collaborative International Dictionary of English v.0.48:

Ostentatious \Os`ten*ta"tious\, a.
   Fond of, or evincing, ostentation; unduly conspicuous;
   pretentious; boastful.
   [1913 Webster]

         Far from being ostentatious of the good you do.
                                                  --Dryden.
   [1913 Webster]

         The ostentatious professions of many years. --Macaulay.
   [1913 Webster] -- Os`ten*ta"tious*ly, adv. --
   Os`ten*ta"tious*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ostentatiously
    adv 1: with ostentation; in an ostentatious manner; "Mr
           Khrushchev ostentatiously wooed and embraced Castro at
           the U.N. general assembly" [syn: ostentatiously,
           showily]