Lewis Short
(adjective) : ĭn-effĭcax, ācis
* Ineffectual, inefficient (post-Aug.).
* With gen.: vox inefficax verborum,unproductive of, unable to produce,Sen. Ira, 1, 3.
* Absol.: ratio,Sen. Ira, 1, 10: dii,id. Ben. 4, 4.— Comp., Plin. 34, 11, 25, § 109: parentes inefficacissimi, i. e. very weak, Inscr. ap. Grut. 415, 10.—Adv.: ĭneffĭcācĭter, ineffectually, in vain, Dig. 49, 8, 2; Cod. Just. 6, 35, 2; Symm. Ep. 6, 53.
Charlton T. Lewis, Charles Short, A Latin Dictionary