Synonyms for Fantastically:

adv.

exceptionally (adverb)
extraordinarily, excellently, peculiarly, strikingly, wonderfully, unusually, exceptionally, outstandingly, notably, novelly, phenomenally, Superiorly.
imaginarily (adverb)
inventively, speculatively, Imaginarily, dreamily, conceptually.
strangely (adverb)
peculiarly, exceptionally, strikingly, unusually.
theoretically (adverb)
suppositionally, Conjecturally, prophetically, theoretically, presumably, hypothetically.

adv

exceptionally (adverb)
extraordinarily, excellently, peculiarly, strikingly, wonderfully, unusually, exceptionally, outstandingly, notably, novelly, phenomenally, Superiorly.
extremely (adverb)
overwhelmingly, distinctly.
imaginarily (adverb)
inventively, speculatively, Imaginarily, dreamily, conceptually.
theoretically (adverb)
speculatively, presumably, Imaginarily, theoretically, prophetically, Conjecturally, suppositionally, hypothetically.

n.

superlatively, good, well, to perfection, great, like a dream, to the best of your ability, ably. incongruous, funny, idiosyncratic, unreal, outlandish, weird, edgy, eccentric, strange, surreal. fantastically (noun)
fabulously.

Other synonyms:

ably, superlatively, great. well. good. Other relevant words:
funny, great, superlatively, fabulously, ably.

Usage examples for fantastically

  1. This " Mediterranean of the Pacific" throughout its length and breadth is adorned with heavily- wooded and fantastically formed islands. – Oregon, Washington and Alaska; Sights and Scenes for the Tourist by E. L. Lomax
  2. All was strange and mazed and quivering in her, her spirit straining away, drawn to him, fantastically confused. – Beyond by John Galsworthy