impossible to please; incapable of being placated
His implacable determination to succeed never wavered despite obstacles.
Vocabulary like implacable appears on the Digital SAT in Words-in-Context questions, where you choose the word that fits a passage's meaning and tone. You can also drill this word with vocabulary flashcards.
force; urge or force (a person) to an action; constrain or motivate
unnoticeable; impossible or difficult to perceive by the mind or senses
extremely dense; preventing especially liquids to pass or diffuse through
disrespectful; characterized by a lightly pert and exuberant quality
calm; not easily perturbed or excited or upset; marked by extreme calm and composure
unaffected; not admitting of passage or capable of being affected
acting without thought
unrighteousness; unrighteousness by virtue of lacking respect for a god