The Collaborative International Dictionary of English v.0.48:

Inconclusive \In`con*clu"sive\, a.
   Not conclusive; leading to no conclusion; not closing or
   settling a point in debate, or a doubtful question; as,
   evidence is inconclusive when it does not exhibit the truth
   of a disputed case in such a manner as to satisfy the mind,
   and put an end to debate or doubt.
   [1913 Webster]

         Arguments . . . inconclusive and impertinent. --South.
   -- In`con*clu"sive*ly, adv. -- In`con*clu"sive*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

inconclusive
    adj 1: not conclusive; not putting an end to doubt or question;
           "an inconclusive reply"; "inconclusive evidence"; "the
           inconclusive committee vote" [ant: conclusive]

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "inconclusive":
   absonant, contradictory, contrary to reason, fallacious, faulty,
   feeble, flawed, flimsy, groundless, illogical, inauthentic,
   incongruous, inconsequent, inconsequential, inconsistent,
   indecisive, indefinite, indeterminate, insubstantial, invalid,
   irrational, loose, nonscientific, not following, not proved, open,
   paralogical, poor, reasonless, self-annulling, self-contradictory,
   self-refuting, senseless, unascertained, unattested, unauthentic,
   unauthenticated, uncertain, uncertified, unconfirmed, unconnected,
   uncorroborated, undemonstrated, undetermined, unestablished,
   unfinished, unfixed, unfounded, unphilosophical, unproved,
   unproven, unreasonable, unresolved, unrigorous, unscientific,
   unsettled, unshown, unsound, unsubstantial, unsubstantiated,
   unsupported, unsupported by evidence, unsustained, untested,
   untried, unvalidated, unverified, weak, without basis,
   without grounds, without reason



Bouvier's Law Dictionary, Revised 6th Ed (1856):

INCONCLUSIVE. What does not put an end to a thing. Inconclusive presumptions
are those which may be overcome by opposing proof; for example, the law
presumes that he who  possesses personal property is the owner of it, but
evidence is allowed to contradict this presumption, and show who is the true
owner. 3 Bouv. Inst. in. 3063.