Read the dictionary definition of insubstantial. All definitions for this word.
1. lacking material form or substance; unreal
1. as insubstantial as a dream
2. an insubstantial mirage on the horizon
2. lacking solidity or strength
1. a flimsy table
2. flimsy construction
3. vinyl siding has become the standard-bearer for cheap, insubstantial construction
3. lacking in nutritive value
1. an insubstantial and unsatisfying meal