"404" meaning in Translingual

{
  "head_templates": [
    {
      "args": {
        "1": "mul",
        "2": "noun"
      },
      "expansion": "404",
      "name": "head"
    }
  ],
  "lang": "Translingual",
  "lang_code": "mul",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Pages with 4 entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Translingual entries with incorrect language header",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "langcode": "mul",
          "name": "Computing",
          "orig": "mul:Computing",
          "parents": [],
          "source": "w"
        }
      ],
      "derived": [
        {
          "roman": "krajina 404",
          "word": "країна 404"
        },
        {
          "roman": "strana 404",
          "word": "страна 404"
        }
      ],
      "glosses": [
        "An error indicating that a web page could not be found."
      ],
      "id": "en-404-mul-noun-qjBayIBK",
      "links": [
        [
          "computing",
          "computing#Noun"
        ]
      ],
      "raw_glosses": [
        "(computing) An error indicating that a web page could not be found."
      ],
      "topics": [
        "computing",
        "engineering",
        "mathematics",
        "natural-sciences",
        "physical-sciences",
        "sciences"
      ]
    }
  ],
  "word": "404"
}

{
  "derived": [
    {
      "roman": "krajina 404",
      "word": "країна 404"
    },
    {
      "roman": "strana 404",
      "word": "страна 404"
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "mul",
        "2": "noun"
      },
      "expansion": "404",
      "name": "head"
    }
  ],
  "lang": "Translingual",
  "lang_code": "mul",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "Pages with 4 entries",
        "Pages with entries",
        "Translingual entries with incorrect language header",
        "Translingual lemmas",
        "Translingual nouns",
        "Translingual palindromes",
        "Translingual terms spelled with numbers",
        "mul:Computing"
      ],
      "glosses": [
        "An error indicating that a web page could not be found."
      ],
      "links": [
        [
          "computing",
          "computing#Noun"
        ]
      ],
      "raw_glosses": [
        "(computing) An error indicating that a web page could not be found."
      ],
      "topics": [
        "computing",
        "engineering",
        "mathematics",
        "natural-sciences",
        "physical-sciences",
        "sciences"
      ]
    }
  ],
  "word": "404"
}