"anyone's guess" meaning in English

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  "lang_code": "en",
  "pos": "noun",
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          "ref": "2011 January 5, Jonathan Stevenson, “Arsenal 0 - 0 Man City”, in BBC:",
          "text": "It was a disappointing way for the game to finish, with Sagna guilty of leaning his head in towards Zabaleta's after a challenge by the touchline, though what the Argentine did to warrant a dismissal is anyone's guess.",
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      ],
      "glosses": [
        "A mystery; something unpredictable."
      ],
      "id": "en-anyone's_guess-en-noun-iGm8OrP2",
      "links": [
        [
          "mystery",
          "mystery"
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        [
          "unpredictable",
          "unpredictable"
        ]
      ],
      "raw_glosses": [
        "(idiomatic) A mystery; something unpredictable."
      ],
      "related": [
        {
          "word": "your guess is as good as mine"
        }
      ],
      "tags": [
        "idiomatic"
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      "translations": [
        {
          "code": "fr",
          "lang": "French",
          "sense": "Translations",
          "word": "mystère"
        },
        {
          "code": "fr",
          "lang": "French",
          "sense": "Translations",
          "tags": [
            "feminine"
          ],
          "word": "surprise"
        },
        {
          "code": "el",
          "lang": "Greek",
          "roman": "entelós avévaio",
          "sense": "Translations",
          "tags": [
            "neuter"
          ],
          "word": "εντελώς αβέβαιο"
        },
        {
          "code": "ru",
          "lang": "Russian",
          "roman": "délo tjómnoje",
          "sense": "Translations",
          "word": "де́ло тёмное"
        }
      ]
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  "word": "anyone's guess"
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  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "your guess is as good as mine"
    }
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        {
          "ref": "2011 January 5, Jonathan Stevenson, “Arsenal 0 - 0 Man City”, in BBC:",
          "text": "It was a disappointing way for the game to finish, with Sagna guilty of leaning his head in towards Zabaleta's after a challenge by the touchline, though what the Argentine did to warrant a dismissal is anyone's guess.",
          "type": "quote"
        }
      ],
      "glosses": [
        "A mystery; something unpredictable."
      ],
      "links": [
        [
          "mystery",
          "mystery"
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        [
          "unpredictable",
          "unpredictable"
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        "(idiomatic) A mystery; something unpredictable."
      ],
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        "idiomatic"
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  "translations": [
    {
      "code": "fr",
      "lang": "French",
      "sense": "Translations",
      "word": "mystère"
    },
    {
      "code": "fr",
      "lang": "French",
      "sense": "Translations",
      "tags": [
        "feminine"
      ],
      "word": "surprise"
    },
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      "code": "el",
      "lang": "Greek",
      "roman": "entelós avévaio",
      "sense": "Translations",
      "tags": [
        "neuter"
      ],
      "word": "εντελώς αβέβαιο"
    },
    {
      "code": "ru",
      "lang": "Russian",
      "roman": "délo tjómnoje",
      "sense": "Translations",
      "word": "де́ло тёмное"
    }
  ],
  "word": "anyone's guess"
}