6
unsubstantiated
5
bottomless(adjective, reason, false, true, senseless)
5
chimerical(adjective, reason, justification)
5
heedless
5
illusory(adjective, reason, justification)
5
imaginary(adjective, reason, justification)
5
uncalled-for(adjective, reason, false, useless, senseless)
4
absurd(adjective, foolish, unreasonable, irrational, illogical)
4
insupportable(adjective, defended, verbal attack)
4
invalid(foolish, unreasonable, reasoning, irrational, illogical)
4
irrational(adjective, foolish, unreasonable, illogical, defended)
4
ridiculous(adjective, foolish, unreasonable, illogical, defended)
4
sophistic(adjective, foolish, unreasonable, irrational, illogical)
4
specious(adjective, foolish, unreasonable, irrational, illogical)
4
speculative
4
vain(adjective, false, empty, worthless, untrue)
3
apocryphal(adjective, error)
3
causeless(adjective, reason, useless, senseless, unwarranted)
3
dead
3
erroneous(adjective, error)
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APASmart Define. (2015). groundless thesaurus. Retrieved September 20, 2026, from https://smartdefine.org/groundless/thesaurus/synonyms
ChicagoSmart Define. 2015. "groundless thesaurus" https://smartdefine.org/groundless/thesaurus/synonyms (accessed September 20, 2026).
HarvardSmart Define 2015, groundless thesaurus, Smart Define, viewed 20 September, 2026, <https://smartdefine.org/groundless/thesaurus/synonyms>.
MLASmart Define. "groundless thesaurus" 14 April 2015. Web. 20 September 2026. <https://smartdefine.org/groundless/thesaurus/synonyms>