In·ef·fi·ca·cy n. Lack of power to produce the desired or proper effect; inefficiency; ineffectualness; futility; uselessness; fruitlessness; as, the inefficacy of medicines or means.
The seeming inefficacy of censures. --Bp. Hall.
The inefficacy was soon proved, like that of many similar medicines. --James Gregory.
n : a lack of efficacy [syn: inefficaciousness] [ant: efficacy]