350 entries under adjective topic. ×

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frangible(weak, delicate, feeble, infirm)
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hallucinatory(strange, negative, fantastic, fantasy)
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illusional(strange, fantasy, unreal)
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illusionary(strange, fantasy, unreal)
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illusive(strange, fantasy, unreal)
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imponderable(light, weak, slight, heavenly)
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improbable(thin, extraordinary, strange, unreasonable)
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inadequate(dull, light, weak, soft)
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inconceivable(thin, extraordinary, belief, unreasonable)
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pale(dull, light, soft, poor)
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phantasmagoric(excellent, gentle, marvelous, vague)
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ramshackle
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sleazy(weak, slight, thin, feeble)
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supernatural(abstract, heavenly, theoretical, immaterial)
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unearthly(abstract, heavenly, theoretical, immaterial)
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unimportant(weak, soft, gentle, mild)
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unworldly(heavenly, immaterial, ghostly, incorporeal)
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vague(excellent, gentle, obscure, negative)
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weakly(strong, weak, delicate, uncertain)
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weightless(light, slight, easy, thin)
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APASmart Define. (2016). unsubstantial thesaurus. Retrieved September 27, 2026, from https://smartdefine.org/unsubstantial/thesaurus/synonyms
ChicagoSmart Define. 2016. "unsubstantial thesaurus" https://smartdefine.org/unsubstantial/thesaurus/synonyms (accessed September 27, 2026).
HarvardSmart Define 2016, unsubstantial thesaurus, Smart Define, viewed 27 September, 2026, <https://smartdefine.org/unsubstantial/thesaurus/synonyms>.
MLASmart Define. "unsubstantial thesaurus" 30 March 2016. Web. 27 September 2026. <https://smartdefine.org/unsubstantial/thesaurus/synonyms>