"thermal coal" meaning in English

{
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "thermal coal (uncountable)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Coal",
          "orig": "en:Coal",
          "parents": [
            "Fossil fuels",
            "Carbon",
            "Energy",
            "Natural resources",
            "Carbon group elements",
            "Nature",
            "Matter",
            "Chemical elements",
            "All topics",
            "Chemistry",
            "Fundamental",
            "Sciences"
          ],
          "source": "w"
        }
      ],
      "coordinate_terms": [
        {
          "word": "metallurgical coal"
        }
      ],
      "glosses": [
        "the type of coal used in coal-fired electrical power plants"
      ],
      "id": "en-thermal_coal-en-noun-LeIg3wOQ",
      "links": [
        [
          "coal",
          "coal"
        ]
      ],
      "synonyms": [
        {
          "word": "steaming coal"
        },
        {
          "word": "steam coal"
        }
      ],
      "tags": [
        "uncountable"
      ]
    }
  ],
  "word": "thermal coal"
}

{
  "coordinate_terms": [
    {
      "word": "metallurgical coal"
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "thermal coal (uncountable)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English uncountable nouns",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Coal"
      ],
      "glosses": [
        "the type of coal used in coal-fired electrical power plants"
      ],
      "links": [
        [
          "coal",
          "coal"
        ]
      ],
      "tags": [
        "uncountable"
      ]
    }
  ],
  "synonyms": [
    {
      "word": "steaming coal"
    },
    {
      "word": "steam coal"
    }
  ],
  "word": "thermal coal"
}