IMPLACABIL'ITY IMPLA'CABLE, adjective [Latin 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.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI