Source : WordNet®

suppositious
     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: {conjectural},
            {divinatory}, {supposed}, {suppositional}, {supposititious}]