implacable
UK[ɪmˈplækəbl]US[ɪmˈpleɪkəbl]
adj
(of a negative feeling or attitude) impossible to change or satisfy; relentless
adj
(of a person) unwilling to stop being angry or hostile
Morpheme Breakdown
im
plac
able
im
not
plac
appease
able
capable of
Etymology
The word 'implacable' has a direct lineage from Latin. It is formed from the Latin adjective implacabilis, which itself is a combination of the negative prefix in- (meaning "not"), the verb placare (meaning "to soothe, appease, or calm"), and the adjectival suffix -abilis (meaning "able to be"). The core semantic journey revolves around the root plac-, which relates to pleasing and pacifying. Thus, the literal meaning is "not able to be appeased or pacified." This concrete sense of an anger or hostility that cannot be soothed evolved seamlessly into the modern abstract meanings describing unyielding negative feelings or an unforgiving, relentless attitude.
Analysis
Structure: im (not) + plac (appease) + able (capable of)
im: Latin origin, a prefix meaning "not" or "without".
plac: Latin origin, from the root plac- meaning "to please, soothe, or appease".
able: Latin origin via French, a suffix meaning "capable of, fit for, or tending to".
Examples
She was implacable in her opposition to the proposed law.
The drought brought implacable heat to the region for months.
Despite their apologies, his anger remained implacable.