Source : Webster's Revised Unabridged Dictionary (1913)

Probably \Prob"a*bly\, adv.
   In a probable manner; in likelihood.

         Distinguish between what may possibly and what will
         probably be done.                        --L'Estrange.

Source : WordNet®

probably
     adv 1: with considerable certainty; without much doubt; "He is
            probably out of the country"; "in all likelihood we
            are headed for war" [syn: {likely}, {in all likelihood},
             {in all probability}, {belike}]
     2: easy to believe on the basis of available evidence; "he
        talked plausibly before the committee"; "he will probably
        win the election" [syn: {credibly}, {believably}, {plausibly}]
        [ant: {incredibly}]