That cannot be pinned down; elusive; uncapturable.(adjective)
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Use "unpindownable" in a sentence
"With this book, the unpindownable Cory commences what I suspect will be a successful 92nd career as a YA author."
"The key thing he revealed is how brilliant a political performer he is: affable, unflappable and unpindownable."
"Why is it, in the 21st century,when we should be making progress, that so many people seem to have handed over their life destiny to either the government (and thus effectively other taxpayers who are providing the benefits and the credits) or some sort of unpindownable other party?"