Synonyms for Unsubstantially:

adv.

immaterially (adverb)
conceptually, Impalpably, imponderably, intangibly, supernaturally, theoretically, spiritually, abstractly, Imaginarily, Ethereally, Immaterially.
lightly (adverb)
Ethereally.
unsubstantially (adverb)
vacuously, vacantly, insignificantly, emptily, Spectrally.

adv

immaterially (adverb)
conceptually, Impalpably, imponderably, intangibly, supernaturally, theoretically, spiritually, abstractly, Imaginarily, Ethereally, Immaterially.
lightly (adverb)
Ethereally.
unsubstantially (adverb)
vacuously, vacantly, insignificantly, emptily, Spectrally.