inconceivable

Etymology

in- + conceivable

adj

1. Unable to be conceived or imagined; unbelievable.
   While the world altered dramatically during the course of her reign, the monarchy did too, though rather more imperceptibly: the walkabouts that increasingly characterised royal appearances, the pop concerts at Buckingham Palace, the throwing open of the royal palaces to visitors – even the paying of income tax, and royal podcasts – would have been inconceivable as innovations at the time Elizabeth came to the throne. September 8 2022, Stephen Bates, “Queen Elizabeth II obituary”, in The Guardian