The Collaborative International Dictionary of English v.0.48:

Manifestly \Man"i*fest*ly\, adv.
   In a manifest manner; obviously; evidently; clearly.
   [1913 Webster]

WordNet (r) 3.0 (2006):

manifestly
    adv 1: unmistakably (`plain' is often used informally for
           `plainly'); "the answer is obviously wrong"; "she was in
           bed and evidently in great pain"; "he was manifestly too
           important to leave off the guest list"; "it is all
           patently nonsense"; "she has apparently been living here
           for some time"; "I thought he owned the property, but
           apparently not"; "You are plainly wrong"; "he is plain
           stubborn" [syn: obviously, evidently, manifestly,
           patently, apparently, plainly, plain]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "manifestly":
   absolutely, actually, apparently, assuredly, certainly, clearly,
   conspicuously, de facto, decidedly, definitely, demonstrably,
   discernibly, distinctly, evidently, explicitly, expressly,
   for a certainty, for real, genuinely, glaringly, in actuality,
   in all conscience, in effect, in fact, in reality, indeed,
   indisputably, indubitably, markedly, noticeably, observably,
   obviously, palpably, patently, perceivably, perceptibly, plainly,
   positively, prominently, pronouncedly, quite, really, recognizably,
   seeably, sensibly, seriously, staringly, starkly, truly,
   unambiguously, unconcealedly, undeniably, undisguisedly,
   undoubtedly, unmistakably, unquestionably, verily, veritably,
   visibly, with clarity, without doubt