- not to be appeased, mollified, or pacified; inexorable: an implacable enemy.
- incapable of being placated or pacified; unappeasable
- inflexible; intractable
early 15c., from Old French implacable, from Latin implacabilis “unappeasable,” from assimilated form of in- “not, opposite of” (see in- (1)) + placabilis “easily appeased” (see placate). Related: Implacably.