Definition of undecidable in US English:



  • 1Not able to be firmly established or refuted.

    1. 1.1Logic (of a proposition or theorem) not able to be proved or disproved.
      • ‘In Undecidable theories Tarski showed that group theory, lattices, abstract projective geometry, closure algebras and others mathematical systems are undecidable.’
      • ‘And we know that 1st order logic is undecidable,’
      • ‘Godel showed that in any formal system adequate for number theory there is an undecidable formula, that is, a formula such that neither it nor its negation can be proved.’
      • ‘All we could achieve by our mathematics would be non-constructive existence proofs that told us that they existed, in much the same manner that we can deduce the existence of undecidable propositions.’
      • ‘Viruses are free to mutate into an infinite variety of functionally equivalent forms, whereas the process of establishing their equivalence is undecidable.’