from
The Collaborative International Dictionary of English v.0.48
Inefficacious \In*ef`fi*ca"cious\, a. [Pref. in- not +
efficacious: cf. F. inefficace, L. inefficax.]
Not efficacious; not having power to produce the effect
desired; inadequate; incompetent; inefficient; impotent.
--Boyle.
[1913 Webster]
The authority of Parliament must become inefficacious .
. . to restrain the growth of disorders. --Burke.
[1913 Webster]
Note: Ineffectual, says Johnson, rather denotes an actual
failure, and inefficacious an habitual impotence to any
effect. But the distinction is not always observed, nor
can it be; for we can not always know whether means are
inefficacious till experiment has proved them
ineffectual. Inefficacious is therefore sometimes
synonymous with ineffectual.
[1913 Webster]