Source : Webster's Revised Unabridged Dictionary (1913)

Tentative \Ten*ta"tive\, a. [L. tentare to try: cf. F. tentatif.
   See {Tempt}.]
   Of or pertaining to a trial or trials; essaying;
   experimental. ``A slow, tentative manner.'' --Carlyle. --
   {Ten*ta"tive*ly}, adv.

Source : WordNet®

tentatively
     adv : in a tentative manner; "we agreed tentatively on a dinner
           date"