inefficacious

1 not producing the desired result his efforts to restore the neglected houseplant back to health were belated and sadly inefficacious Synonyms counterproductive, feckless, hamstrung, ineffectual, ineffective, inefficient, inexpedientRelated Words abortive, bootless, fruitless, futile, nonproductive, pointless, profitless, unavailing, unproductive, unprofitable, unsuccessful, useless, worthlessNear Antonyms availing, beneficial, helpful, productive, profitable, successful, useful, worthwhileAntonyms effective, effectual, efficacious, efficient, expedient, operant, ultraefficient

2 producing no results an inefficacious medication for a rare form of tuberculosis Synonyms abortive, barren, bootless, empty, fruitless, ineffective, ineffectual, futile, otiose, profitless, unavailing, unproductive, unprofitable, unsuccessful, useless, vainRelated Words hollow, idle, meaningless, pointless, valueless, worthless; hopeless, impossible, lost, no-win, unattainable; inadequate, insufficient, lacking, wanting; counterproductiveNear Antonyms meaningful, worthwhile; adequate, sufficient; applicable, feasible, functional, practicable, practical, realizable, usable (also useable), workableAntonyms deadly, effective, effectual, efficacious, efficient, fruitful, potent, productive, profitable, successful, virtuous