"pigs may fly" meaning in English

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  "lang_code": "en",
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          "ref": "1913, Arthur Conan Doyle, “(please specify the page)”, in The Poison Belt […], London; New York, N.Y.: Hodder and Stoughton, →OCLC:",
          "text": "\"Pigs may fly. Yes, sir, pigs may fly - but they don't. It is not worth arguing with you. Challenger has filled you with his nonsense and you are both incapable of reason.\"",
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      "glosses": [
        "Alternative form of pigs might fly"
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  "lang_code": "en",
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