Here’s a perfect word to characterize someone who is unreasonably stubborn, persistent, or impossible to please…
What it Means: Describing someone who cannot be appeased, whose views or actions cannot be changed.
How to Use It: “We have tried every reasonable option to make the owners of the property happy with our plans, but they remain implacable.”
About the Word: It comes from the Latin word placare, which means “to calm” — pretty much what the word “placate” means in English. Another form of placare spawned the word “placid,” meaning peaceful, as well as “placebo,” which means a pill that makes you happy even though it doesn’t have any real medicinal value.
How this Word Works for You: “Implacable” is a muscular word that expresses the notion that nothing will make the other party happy. It’s an uncannily perfect (and properly sophisticated) way of characterizing an opponent as a whiny toddler who just can’t be pleased. Even people who might not be able to summon a precise definition of “implacable” generally realize that it carries negative baggage, so use the word when you want to gain an upper hand over someone you truly believe unreasonable. “Relentless,” for example, can be construed to be admiration, so don’t use that word if you want to invoke the toddler image. “Implacable” adds that appropriate spoiled-child disdain to your assessment.