unsubstantial

UK: /ˌʌnsəbˈstænʃəl/

US: /ˌʌnsəbˈstænʃəl/

US: (un′səb stan′shəl)

WordReference Random House Learner's Dictionary of American English © 2025

un•sub•stan•tial /ˌʌnsəbˈstænʃəl/   adj. 

1. having no foundation in fact.
2. lacking material substance.
3. lacking strength or solidity;
   flimsy.

WordReference Random House Unabridged Dictionary of American English © 2025

un•sub•stan•tial  (un′səb stan′shəl), adj. 

1. not substantial;
   having no foundation in fact;
   fanciful;
   insubstantial:
   an unsubstantial argument; unsubstantial hopes.
2. without material substance:
   an unsubstantial ghost.
3. lacking material substance;
   materially paltry:
   an unsubstantial dinner of bread and cheese.
4. lacking strength or solidity;
   flimsy:
   an unsubstantial wall of cardboard.

• 1425–75; late Middle English; see un-¹, substantial

un′sub•stan′ti•al′i•ty, n. 
un′sub•stan′tial•ly, adv. 

Collins Concise English Dictionary © HarperCollins Publishers::

unsubstantial / ˌʌnsəbˈstænʃəl/ adjective

1. lacking weight, strength, or firmness
2. (esp of an argument) of doubtful validity
3. of no material existence or substance; unreal

ˌunsubˈstantially adverb