The Collaborative International Dictionary of English v.0.48:

Abortive \A*bor"tive\, a. [L. abortivus, fr. aboriri. See
   Abort, v.]
   1. Produced by abortion.as, an abortive child. [R.]
      [1913 Webster + AS]

   2. Made from the skin of a still-born animal; as, abortive
      vellum. [Obs.]
      [1913 Webster]

   3. Rendering fruitless or ineffectual. [Obs.] "Plunged in
      that abortive gulf." --Milton.
      [1913 Webster]

   4. Coming to naught; failing in its effect; miscarrying;
      fruitless; unsuccessful; as, an abortive attempt. "An
      abortive enterprise." --Prescott.
      [1913 Webster]

   5. (Biol.) Imperfectly formed or developed; rudimentary;
      sterile; as, an abortive organ, stamen, ovule, etc. AS
      [1913 Webster]

   6. (Med.)
      (a) Causing abortion; as, abortive medicines. --Parr. AS
      (b) Cutting short the period of an illness; as, abortive
          treatment of typhoid fever.
          [1913 Webster + AS]

The Collaborative International Dictionary of English v.0.48:

Abortive \A*bor"tive\, n.
   1. That which is born or brought forth prematurely; an
      abortion. [Obs.] --Shak.
      [1913 Webster]

   2. A fruitless effort or issue. [Obs.]
      [1913 Webster]

   3. (Med.) A medicine to which is attributed the property of
      causing abortion; -- also called an abortifacient.
      --Dunglison.
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

abortive
    adj 1: failing to accomplish an intended result; "an abortive
           revolt"; "a stillborn plot to assassinate the President"
           [syn: abortive, stillborn, unsuccessful]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "abortive":
   barren, bootless, failed, failing, fruitless, futile, gainless,
   immature, ineffective, ineffectual, inefficacious, lame, manque,
   miscarried, miscarrying, nonremunerative, of no effect, otiose,
   profitless, rewardless, sterile, stickit, stillborn, successless,
   unavailable, unavailing, unformed, unfortunate, unmatured,
   unproductive, unprofitable, unremunerative, unrewarding, unripe,
   unsuccessful, useless, vain