Source : Webster's Revised Unabridged Dictionary (1913)

Conjectural \Con*jec"tur*al\, a. [L. conjecturalis: cf. F.
   conjectural.]
   Dependent on conjecture; fancied; imagined; guessed at;
   undetermined; doubtful.

         And mak'st conjectural fears to come into me. --Shak.

         A slight expense of conjectural analogy. --Hugh Miller.

         Who or what such editor may be, must remain
         conjectural.                             --Carlyle.

Source : WordNet®

conjectural
     adj : based primarily on surmise rather than adequate evidence;
           "theories about the extinction of dinosaurs are still
           highly conjectural"; "the supposed reason for his
           absence"; "suppositious reconstructions of dead
           languages"; "supposititious hypotheses" [syn: {divinatory},
            {supposed}, {suppositional}, {suppositious}, {supposititious}]