implacable

adjective

im·​pla·​ca·​ble (ˌ)im-ˈpla-kə-bəl  -ˈplā- 

: not placable : not capable of being appeased, significantly changed, or mitigated

an implacable enemy

implacability

(ˌ)im-ˌpla-kə-ˈbi-lə-tē 

-ˌplā-

noun

implacably

(ˌ)im-ˈpla-kə-blē 

-ˈplā-

adverb

Did you know?

Implacable is rooted in Latin placare, meaning "to soothe," but its im- prefix is a variant of the negating prefix in- (as in inactive) and it signals that there’s nothing warm and fuzzy here. Someone or something described as implacable cannot be soothed, which usually means trouble: implacable is most often attached to words like foe, enemy, hatred and hostility. The opposite of implacable is, of course, placable; it means "easily soothed," but sadly isn’t called upon very often. Another placare word is likely more familiar. Placate means "to soothe or appease"; it’s frequently applied when an angry person is made to feel less so.

Synonyms of implacable

• stubborn
• adamant
• steadfast

Examples of implacable in a Sentence

He has an implacable hatred for his political opponents.

an implacable judge who knew in his bones that the cover-up extended to the highest levels of government

Recent Examples on the Web

But absent an oil-rich ally, like Russia or Venezuela, and faced with an implacable enemy, Cuban officials may have no choice but to bring Cuba back into the orbit of American power, at least for now. —Joseph J. Gonzalez, The Conversation, 23 Mar. 2026

But as all the world knows, Edmond Dantès did rise again, transformed from an innocent young sailor into that courtly yet implacable avenger, the Count of Monte Cristo. —Michael Dirda, The New York Review of Books, 19 Mar. 2026

Within a year, Hezbollah was established, becoming one of Israel’s most implacable enemies. —Ron Kampeas, Sun Sentinel, 2 Mar. 2026

Duvall as Hagen has poured a drink before the revelation, but Brando joins him with an awareness of trouble, and the news is given and received with implacable dignity by both. —Fred Schruers, IndieWire, 16 Feb. 2026

Word History

Etymology

Middle English, from Latin implacabilis, from in- + placabilis placable

First Known Use

15th century, in the meaning defined above

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Kids Definition

implacable

adjective

im·​pla·​ca·​ble (ˈ)im-ˈplak-ə-bəl  -ˈplā-kə- 

: not possible to please, satisfy, or change

an implacable enemy

implacability

-ˌplak-ə-ˈbil-ət-ē 

-ˌplā-kə-

noun

implacably

-ˈplak-ə-blē 

-ˈplā-kə-

adverb