Im-plā'ca-ble, a.
a. [Fr. & Sp. implacable, It. implacabile, Lat. implacabilis, from prefix im, for in, not, and placabilis, placable.]
Sense 1. Not placable; not to be appeased; incapable of being pacified; inexorable; stubborn or constant in enmity; as, an implacable prince. “I see thou art implacable.” Milton. “An object of implacable enmity.” Macaulay.
Sense 2. Incapable of being relieved or quieted; inextinguishable. [Rare.]
Which wrought them pain Implacable, and many a dolorous groan. Milton.
Synonyms—Unappeasable; inexorable; irreconcilable; unrelenting; relentless.