The Collaborative International Dictionary of English v.0.48:

Inadequate \In*ad"e*quate\, a. [Pref. in- not + adequate: cf. F.
   inad['e]quat.]
   Not adequate; unequal to the purpose; insufficient;
   deficient; as, inadequate resources, power, conceptions,
   representations, etc. --Dryden. -- In*ad"e*quate*ly, adv.
   -- In*ad"e*quate*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

inadequately
    adv 1: in an inadequate manner or to an inadequate degree; "the
           temporary camps were inadequately equipped" [ant:
           adequately]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "inadequately":
   by halves, defectively, deficiently, dissatisfactorily, faultily,
   imperfectly, in half measures, in installments, inadeptly,
   inadmissibly, inaptly, incapably, incompetently, incompletely,
   inefficiently, ineptly, inexpertly, insufficiently, intolerably,
   objectionably, partially, poorly, unacceptably, unaptly, undeftly,
   undesirably, undexterously, unfacilely, unfitly, ungratifyingly,
   unproficiently, unsatisfactorily, unsatisfyingly, unskillfully,
   unsubstantially, unsuitably