"dead oil" meaning in English

{
  "forms": [
    {
      "form": "dead oils",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "-",
        "2": "s"
      },
      "expansion": "dead oil (usually uncountable, plural dead oils)",
      "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": "Oil industry",
          "orig": "en:Oil industry",
          "parents": [
            "Industries",
            "Petroleum",
            "Business",
            "Fossil fuels",
            "Liquids",
            "Economics",
            "Society",
            "Carbon",
            "Energy",
            "Natural resources",
            "Matter",
            "Social sciences",
            "All topics",
            "Carbon group elements",
            "Nature",
            "Chemistry",
            "Sciences",
            "Fundamental",
            "Chemical elements"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "The heavy oil obtained in the distillation of coal tar, containing phenol, naphthalus, etc."
      ],
      "id": "en-dead_oil-en-noun-OFixl0Bs",
      "links": [
        [
          "phenol",
          "phenol"
        ]
      ],
      "tags": [
        "uncountable",
        "usually"
      ]
    }
  ],
  "word": "dead oil"
}

{
  "forms": [
    {
      "form": "dead oils",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "-",
        "2": "s"
      },
      "expansion": "dead oil (usually uncountable, plural dead oils)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English uncountable nouns",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Oil industry"
      ],
      "glosses": [
        "The heavy oil obtained in the distillation of coal tar, containing phenol, naphthalus, etc."
      ],
      "links": [
        [
          "phenol",
          "phenol"
        ]
      ],
      "tags": [
        "uncountable",
        "usually"
      ]
    }
  ],
  "word": "dead oil"
}