adjective
- not substantial; having no foundation in fact; fanciful; insubstantial: an unsubstantial argument; unsubstantial hopes.
- without material substance: an unsubstantial ghost.
- lacking material substance; materially paltry: an unsubstantial dinner of bread and cheese.
- lacking strength or solidity; flimsy: an unsubstantial wall of cardboard.
adjective
- lacking weight, strength, or firmness
- (esp of an argument) of doubtful validity
- of no material existence or substance; unreal
adj.mid-15c., from un- (1) “not” + substantial.