Implacable [im-PLAK-ə-bəl]

Part of speech: adjective
Origin: French, 16th century

1. Unable to be placated.
2. Relentless; unstoppable.

Examples of implacable in a sentence

“Charlie tried appealing to the principal to cancel his suspension for pranks and mischief, but she was implacable.”

“When it comes to enforcing our teenage son’s nightly curfew, my husband and I are implacable.”