Source : Webster's Revised Unabridged Dictionary (1913)

Conjecturally \Con*jec`tur*al"ly\, n.
   That which depends upon guess; guesswork. [R.] --Sir T.
   Browne.

Conjecturally \Con*jec`tur*al*ly\, adv.
   In a conjectural manner; by way of conjecture. --Boyle.