"containment line" meaning in English

{
  "forms": [
    {
      "form": "containment lines",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "containment line (plural containment lines)",
      "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": "Firefighting",
          "orig": "en:Firefighting",
          "parents": [
            "Emergency services",
            "Fire",
            "Public safety",
            "Combustion",
            "Light sources",
            "Public administration",
            "Security",
            "Chemical processes",
            "Light",
            "Government",
            "Society",
            "Nature",
            "Energy",
            "Politics",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A linear area which has been cleared of inflammable material in order to prevent a fire from spreading across it."
      ],
      "id": "en-containment_line-en-noun-4ADuZtxY",
      "links": [
        [
          "firefighting",
          "firefighting"
        ],
        [
          "inflammable",
          "inflammable"
        ]
      ],
      "raw_glosses": [
        "(firefighting) A linear area which has been cleared of inflammable material in order to prevent a fire from spreading across it."
      ],
      "topics": [
        "firefighting",
        "government"
      ]
    }
  ],
  "word": "containment line"
}

{
  "forms": [
    {
      "form": "containment lines",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "containment line (plural containment lines)",
      "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:Firefighting"
      ],
      "glosses": [
        "A linear area which has been cleared of inflammable material in order to prevent a fire from spreading across it."
      ],
      "links": [
        [
          "firefighting",
          "firefighting"
        ],
        [
          "inflammable",
          "inflammable"
        ]
      ],
      "raw_glosses": [
        "(firefighting) A linear area which has been cleared of inflammable material in order to prevent a fire from spreading across it."
      ],
      "topics": [
        "firefighting",
        "government"
      ]
    }
  ],
  "word": "containment line"
}