\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.