unfalsifiable

/ʌnˈfɔlsəˌfaɪəbəl/
adjective
  1. Not able to be proven false; impossible to test or disprove.
    • Some philosophical claims are unfalsifiable because they cannot be tested by experiments.
    • Scientists prefer theories that are falsifiable over unfalsifiable ones.
    • The conspiracy theory was unfalsifiable, as any evidence against it was called part of the cover-up.