1. unable to be appeased, pacified, or satisfied; relentless in hostility or determination

Examples

• The dictator was an implacable enemy of democracy.
• She faced her critics with implacable determination.
• His implacable hatred lasted for decades.
• The storm showed implacable fury throughout the night.
• Despite numerous apologies, she remained implacable.
• The prosecutor pursued the case with implacable resolve.