1. Lacking material form or substance; unreal
   "as insubstantial as a dream"; "an insubstantial mirage on the horizon"
   - unsubstantial, unreal 
2. Lacking in nutritive value
   - jejune

See also: aerial, aeriform, aery, airy, ethereal, immaterial, insubstantiality, nonmaterial, shadowy, solidness, stringy, substantiality, substantialness, unwholesome, wraithlike

Antonym: substantial

• Fijis
• filaggrin
• filago
• Filago germanica
• filagree
• filament
• filamentlike
• filamentous
• filar
• filaree
• filaria
• filarial
• filariasis
• filariid
• Filariidae
• filature
• filbert
• filch
• file
• file allocation table
• file away
• file cabinet
• file clerk
• file folder
• file format