Source : Webster's Revised Unabridged Dictionary (1913)

Argumentative \Ar`gu*men"ta*tive\, a.
   1. Consisting of, or characterized by, argument; containing a
      process of reasoning; as, an argumentative discourse.

   2. Adductive as proof; indicative; as, the adaptation of
      things to their uses is argumentative of infinite wisdom
      in the Creator. [Obs.]

   3. Given to argument; characterized by argument;
      disputatious; as, an argumentative writer.
      --{Ar`gu*men"ta*tive*ly}, adv. --
      {Ar`gu*men"ta*tive*ness}, n.

Source : WordNet®

argumentative
     adj : given to or characterized by argument; "an argumentative
           discourse"; "argumentative to the point of being
           cantankerous"; "an intelligent but argumentative child"
           [ant: {unargumentative}]