• (RP) IPA: /ɪmˈplækəb(ə)l/, /-ˈpleɪ-/
• (GA) IPA: /ɪmˈplækəbəl/

implacable

1. Not able to be placated or appeased.

   Synonyms: impacable, irreconcilable, unassuageable, unplacable, unpleasable

   Antonyms: appeasable, assuageable, pacable, pacifiable, placable

   • c. 1601–1602, William Shakespeare, “Twelfe Night, or VVhat You VVill”, in Mr. William Shakespeares Comedies, Histories, & Tragedies: Published According to the True Originall Copies (First Folio), London: Printed by Isaac Iaggard, and Ed[ward] Blount, published 1623, OCLC 606515358 ↗, [Act III, scene iv], page 269 ↗:

     He is knight dubb'd with vnhatche'd Rapier, and on carpet conſideration, but he is a diuell in priuate brawl#English|brall, soules and bodies hath he diuorc'd three, and his incenſement at this moment is ſo implacable, that ſatisfaction can be none, but by pangs of death and ſepulcher: Hob, nob, is his word: giu't or take't.

2. Impossible to prevent or stop#Verb|stop; inexorable, unrelenting#Adjective|unrelenting, unstoppable.

   Synonyms: relentless, unremitting, unyielding

3. Adamant; immovable.
   • 1678, John Bunyan, The Pilgrim’s Progress from This World, to That which is to Come: […], London: Printed for Nath[aniel] Ponder […], OCLC 228725984 ↗; reprinted in The Pilgrim’s Progress (The Noel Douglas Replicas), London: Noel Douglas, […], 1928, OCLC 5190338 ↗, page 84 ↗:

     Indeed Cain hated his Brother, becauſe his own works were evil, and his Brothers righteous; and if thy Wife and Children have been offended with thee for this, they thereby ſhew themſelves to be implacable to good; and thou haſt delivered thy ſoul from their blood.

• German: unversöhnlich
• Italian: implacabile
• Portuguese: implacável
• Russian: непримири́мый
• Spanish: implacable

• French: implacable, irréductible
• Italian: implacabile
• Russian: неумолимый
• Spanish: implacable

• German: unerbittlich
• Russian: непрекло́нный
• Spanish: implacable, tenaz