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.