In‐ef″fi‐ca‐cy (?), n. [L. inefficacia. See In- not, and Efficacy.] Want 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.