Dictionary.net

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"

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"

Fraudulently substituted for something else; not being what is purports to be; not genuine; spurious; counterfeit; as, a supposititious child; a supposititious writing.

Suppositional; hypothetical.

Put by trick in the place of another: spurious: imaginary.

Fraudulently substituted; not genuine; spurious.

Supposed; fraudulent.