Synonyms|412Antonyms|83|Broader|4Narrower|1Related|376
5
feeble
5
incapable
5
inefficacious
4
ineffective
4
inefficient
4
unproductive
3
unqualified
3
unsuccessful
3
useless
2
fruitless
2
futile
2
ineffectual
2
not helpful
1
abortive
1
awkward
1
barren
1
baseless
1
bootless
1
bungling
1
bushed
For more, visit Efficacious on Power Thesaurus
10 years ago|1.1k views|share |citing 
APASmart Define. (2015). efficacious thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/efficacious/thesaurus/antonyms
ChicagoSmart Define. 2015. "efficacious thesaurus" https://smartdefine.org/efficacious/thesaurus/antonyms (accessed September 22, 2026).
HarvardSmart Define 2015, efficacious thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/efficacious/thesaurus/antonyms>.
MLASmart Define. "efficacious thesaurus" 13 October 2015. Web. 22 September 2026. <https://smartdefine.org/efficacious/thesaurus/antonyms>