inconceivable

From in- +‎ conceivable.

• IPA^(key): /ɪn.kənˈsiː.və.bl̩/

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inconceivable (comparative more inconceivable, superlative most inconceivable)

1. Unable to be conceived or imagined; unbelievable.
   • 2022 September 8, Stephen Bates, “Queen Elizabeth II obituary”, in The Guardian‎:

     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.

• conceivable

• inconceivability
• inconceivableness