2
ineffective(adjective, strong, fit, successful)
2
inefficient(adjective, sound, well, competent, wasteful)
2
inutile
2
otiose
2
destructive
2
detrimental
2
harmful(adjective, bad, awkward, useless)
2
hopeless
2
inconvenient(adjective, bad, awkward, useless)
2
injurious(adjective, bad, awkward, useless)
2
meaningless(adjective, reasonable, use, value, worth)
2
negative
2
non-beneficial(adjective, gain, benefit, effect, result)
2
nonfunctional
2
trivial(adjective, important, substantial, serious)
2
unhelpful(adjective, bad, awkward, useless, helpful)
2
unimportant(adjective, value, important, substantial)
2
unsuitable(adjective, bad, awkward, useless)
2
unsustainable
2
unuseable
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APASmart Define. (2016). useful thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/useful/thesaurus/antonyms
ChicagoSmart Define. 2016. "useful thesaurus" https://smartdefine.org/useful/thesaurus/antonyms (accessed September 24, 2026).
HarvardSmart Define 2016, useful thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/useful/thesaurus/antonyms>.
MLASmart Define. "useful thesaurus" 5 January 2016. Web. 24 September 2026. <https://smartdefine.org/useful/thesaurus/antonyms>