implacable

a. [ L. implacabilis; pref. im- not + placabilis: cf. F. implacable. See Placable. ] 1. Not placable; not to be appeased; incapable of being pacified; inexorable; as, an implacable prince. [ 1913 Webster ]

I see thou art implacable. Milton. [ 1913 Webster ]

An object of implacable enmity. Macaulay. [ 1913 Webster ]

2. Incapable of being relieved or assuaged; inextinguishable. [ R. ] [ 1913 Webster ]

O! how I burn with implacable fire. Spenser. [ 1913 Webster ]

Which wrought them pain
Implacable, and many a dolorous groan. Milton.

Syn. -- Unappeasable; inexorable; irreconcilable; unrelenting; relentless; unyielding. [ 1913 Webster ]