19
groundless(adjective, reason, foolish, true, crazy)
17
unsound(adjective, wrong, fake, false, counterfeit)
15
baseless(adjective, false, foolish, true, crazy)
15
unwarranted(adjective, right, reasonable, true, untrue)
12
fallacious(adjective, wrong, fake, false, counterfeit)
11
unjustifiable(adjective, unwarranted, defended, verbal attack)
10
idle(adjective, false, true, hollow, unwarranted)
10
invalid(adjective, wrong, fake, false, counterfeit)
9
unjustified(adjective, unwarranted, untrue, flimsy, wanton)
9
untenable(adjective, false, defended, verbal attack)
8
faulty(adjective, wrong, fake, false, counterfeit)
7
false(adjective, wrong, fake, counterfeit, unreasonable)
7
gratuitous(adjective, unwarranted, untrue, flimsy, necessary)
7
illogical(adjective, wrong, false, unreasonable, incorrect)
7
unreasonable(adjective, foolish, irrational, unwarranted, illogical)
7
unsustainable(adjective, defended, verbal attack)
7
untrue(adjective, wrong, fake, false, counterfeit)
6
indefensible(adjective, senseless, unwarranted, wanton, gratuitous)
6
specious(adjective, wrong, fake, false, counterfeit)
6
unsubstantiated
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APASmart Define. (2015). unfounded thesaurus. Retrieved September 20, 2026, from https://smartdefine.org/unfounded/thesaurus/synonyms
ChicagoSmart Define. 2015. "unfounded thesaurus" https://smartdefine.org/unfounded/thesaurus/synonyms (accessed September 20, 2026).
HarvardSmart Define 2015, unfounded thesaurus, Smart Define, viewed 20 September, 2026, <https://smartdefine.org/unfounded/thesaurus/synonyms>.
MLASmart Define. "unfounded thesaurus" 14 April 2015. Web. 20 September 2026. <https://smartdefine.org/unfounded/thesaurus/synonyms>