| Inefficacious (a.) Not efficacious; not having power to produce the effect desired; inadequate; incompetent; inefficient; impotent. Thesaurus Entries barren, bootless, failed, failing, fruitless, futile, gainless, immature, ineffective, ineffectual, inefficacious, lame, manque, miscarried, miscarrying, nonremunerative, of no effect, otiose, profitless, rewardless, sterile, stickit, stillborn, successless, unavailable, unavailing, unformed, unfortunate, unmatured, unproductive, unprofitable, unremunerative, unrewarding, unripe, unsuccessful, useless, vain |