failing to produce the desired effect
WordReference Random House Unabridged Dictionary of American English © 2026
in•ef•fi•ca•cious
(in′ef i kā′shəs),USA pronunciation adj.
in′ef•fi•ca′cious•ly, adv.
in′ef•fi•ca′cious•ness, in•ef•fi•cac•i•ty
(in′ef i kas′i tē),USA pronunciation n.
- not able to produce the desired effect; ineffective.
- in-3 + efficacious 1650–60
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