Lacking material substance; insubstantial.(adjective)
Lacking firmness or strength; flimsy.(adjective)
Lacking basis in fact.(adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "unsubstantial" in a sentence
""Something like a London fog" it has been called, "only a dust fog," – an animated fog in which everything unsubstantial is fair prey."
"Even before the protests, female political power and representation in Mubarak's Egypt was unsubstantial and token at best."
"To say that Colbert's testimony was surprisingly unsubstantial, if funny, would be unfair, because it would imply we expected celebrity testimony before congress to be anything other than unsubstantial."