Not placable; not to be appeased; incapable of being pacified; inexorable; as, an implacable prince
If you say that someone is implacable, you mean that they have very strong feelings of hostility or disapproval which nobody can change. the threat of invasion by a ruthless and implacable enemy + implacably im·plac·ably His union was implacably opposed to the privatization of the company. very determined to continue opposing someone or something (implacabilis, from placabilis )