IPA: //səbˈstænsləs//
KK: /sʌbˈstænsləs/
Lacking physical substance or material; not solid or real.
The idea seemed substanceless, floating without any real support.
Substanceless → It is formed from "substance" (from Latin *substantia*, meaning that which stands under or exists) and "-less" (meaning without). The word "substanceless" means lacking substance or material existence.
Think of 'substance' as something that exists or stands under, and remember that 'substanceless' means without that existence.