- insubstantial, unsubstantial, unreal - lacking material form or substance; unreal; "as insubstantial as a dream"; "an insubstantial mirage on the horizon"
Antonyms: substantial, real, material
- insubstantial, jejune - lacking in nutritive value; "the jejune diets of the very poor"
Antonym: wholesome (indirect, via unwholesome)