implacable

/-ˈpleɪ-/

adjective

Meaning

Not able to be placated or appeased.
Impossible to prevent or stop; inexorable, unrelenting, unstoppable.
Adamant; immovable.

Synonyms

impacable,

irreconcilable,

unassuageable,

unplacable,

unpleasable,

relentless,

unremitting,

unyielding