"coal gap" meaning in English

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  "lang_code": "en",
  "pos": "noun",
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        {
          "kind": "topical",
          "langcode": "en",
          "name": "Coal",
          "orig": "en:Coal",
          "parents": [
            "Fossil fuels",
            "Carbon",
            "Energy",
            "Natural resources",
            "Carbon group elements",
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      "glosses": [
        "The time period with few coal deposits from the Permian to middle Jurassic."
      ],
      "id": "en-coal_gap-en-noun-UYWWvhfn",
      "links": [
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          "geology",
          "geology"
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        [
          "coal",
          "coal"
        ],
        [
          "Permian",
          "Permian"
        ],
        [
          "Jurassic",
          "Jurassic"
        ]
      ],
      "raw_glosses": [
        "(geology) The time period with few coal deposits from the Permian to middle Jurassic."
      ],
      "tags": [
        "uncountable"
      ],
      "topics": [
        "geography",
        "geology",
        "natural-sciences"
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    }
  ],
  "word": "coal gap"
}

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  "lang_code": "en",
  "pos": "noun",
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        "en:Coal",
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      "glosses": [
        "The time period with few coal deposits from the Permian to middle Jurassic."
      ],
      "links": [
        [
          "geology",
          "geology"
        ],
        [
          "coal",
          "coal"
        ],
        [
          "Permian",
          "Permian"
        ],
        [
          "Jurassic",
          "Jurassic"
        ]
      ],
      "raw_glosses": [
        "(geology) The time period with few coal deposits from the Permian to middle Jurassic."
      ],
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        "uncountable"
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        "geography",
        "geology",
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  "word": "coal gap"
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