"gray literature" meaning in English

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      "expansion": "gray literature (uncountable)",
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  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "grey literature"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "American English",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
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        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "Alternative spelling of grey literature"
      ],
      "id": "en-gray_literature-en-noun-U6H2iSuH",
      "links": [
        [
          "grey literature",
          "grey literature#English"
        ]
      ],
      "raw_glosses": [
        "(chiefly US) Alternative spelling of grey literature"
      ],
      "tags": [
        "US",
        "alt-of",
        "alternative",
        "uncountable"
      ]
    }
  ],
  "word": "gray literature"
}

{
  "head_templates": [
    {
      "args": {
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      "expansion": "gray literature (uncountable)",
      "name": "en-noun"
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  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "grey literature"
        }
      ],
      "categories": [
        "American English",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English uncountable nouns",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "glosses": [
        "Alternative spelling of grey literature"
      ],
      "links": [
        [
          "grey literature",
          "grey literature#English"
        ]
      ],
      "raw_glosses": [
        "(chiefly US) Alternative spelling of grey literature"
      ],
      "tags": [
        "US",
        "alt-of",
        "alternative",
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  ],
  "word": "gray literature"
}