implacable

IMPLA'CABLE, a. [L. implacabilis; in and placabilis, from placo, to appease.]

1. Not to be appeased; that can not be pacified and rendered peaceable; inexorable; stubborn or constant in enmity; as an implacable prince.

2. Not to be appeased or subdued; as implacable anger; implacable enmity, malice or revenge.