Antonyms of adv possibly

1 of 2 senses of possibly

Sense 2
possibly -- (to a degree possible of achievement or by possible means; "they can't possibly get here in time for the funeral?")
       Antonym of impossibly (Sense 1)
      => impossibly -- (to a degree impossible of achievement; "long thought to be an impossibly difficult operation"; "impossibly far from sources of supply")

Synonyms of adv possibly

2 senses of possibly

Sense 1
possibly, perchance, perhaps, maybe, mayhap, peradventure -- (by chance; "perhaps she will call tomorrow"; "we may possibly run into them at the concert"; "it may peradventure be thought that there never was such a time")

Sense 2
possibly -- (to a degree possible of achievement or by possible means; "they can't possibly get here in time for the funeral?")