"third cover" meaning in English

{
  "etymology_text": "It sequentially follows the first two \"covers\" (the front cover and inside front cover) and precedes the back cover or fourth cover.",
  "forms": [
    {
      "form": "third covers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "third cover (plural third covers)",
      "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": "topical",
          "langcode": "en",
          "name": "Advertising",
          "orig": "en:Advertising",
          "parents": [
            "Business",
            "Marketing",
            "Economics",
            "Society",
            "Social sciences",
            "All topics",
            "Sciences",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "text": "Coordinate term: fourth cover"
        }
      ],
      "glosses": [
        "The inside back cover of a publication."
      ],
      "id": "en-third_cover-en-noun-S87ndi15",
      "links": [
        [
          "advertising",
          "advertising#Noun"
        ],
        [
          "inside",
          "inside"
        ],
        [
          "back cover",
          "back cover"
        ],
        [
          "publication",
          "publication"
        ]
      ],
      "raw_glosses": [
        "(advertising) The inside back cover of a publication."
      ],
      "topics": [
        "advertising",
        "business",
        "marketing"
      ]
    }
  ],
  "word": "third cover"
}

{
  "etymology_text": "It sequentially follows the first two \"covers\" (the front cover and inside front cover) and precedes the back cover or fourth cover.",
  "forms": [
    {
      "form": "third covers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "third cover (plural third covers)",
      "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",
        "en:Advertising"
      ],
      "examples": [
        {
          "text": "Coordinate term: fourth cover"
        }
      ],
      "glosses": [
        "The inside back cover of a publication."
      ],
      "links": [
        [
          "advertising",
          "advertising#Noun"
        ],
        [
          "inside",
          "inside"
        ],
        [
          "back cover",
          "back cover"
        ],
        [
          "publication",
          "publication"
        ]
      ],
      "raw_glosses": [
        "(advertising) The inside back cover of a publication."
      ],
      "topics": [
        "advertising",
        "business",
        "marketing"
      ]
    }
  ],
  "word": "third cover"
}