Learn That Word

Synonyms for Insubstantial (same or very similar meaning)

WordNet sense 1 (lacking in nutritive value):
jejune

WordNet sense 2 (detrimental to physical or moral well-being):
unwholesome

WordNet sense 3 (characterized by lightness and insubstantiality; as impalpable or intangible as air):
aerial, airy, aerial

WordNet sense 4 (lacking material form or substance; unreal):
unreal, unsubstantial


From the ODE community, based on WordNetadd/edit