"Underground Railroad" meaning in English

{
  "forms": [
    {
      "form": "the Underground Railroad",
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "Underground Railway",
      "tags": [
        "alternative"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "def": "1",
        "head": "Underground Railroad"
      },
      "expansion": "the Underground Railroad",
      "name": "en-proper noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "name",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "langcode": "en",
          "name": "History of the United States",
          "orig": "en:History of the United States",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "langcode": "en",
          "name": "Slavery",
          "orig": "en:Slavery",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "langcode": "en",
          "name": "Transport",
          "orig": "en:Transport",
          "parents": [],
          "source": "w"
        }
      ],
      "derived": [
        {
          "word": "underground railroad"
        }
      ],
      "glosses": [
        "The pre-American Civil War anti-slavery resistance movement dedicated to helping escaped slaves to reach safe territory."
      ],
      "id": "en-Underground_Railroad-en-name-PY~fmS8l",
      "links": [
        [
          "American Civil War",
          "American Civil War"
        ],
        [
          "slavery",
          "slavery"
        ],
        [
          "resistance",
          "resistance"
        ],
        [
          "movement",
          "movement"
        ]
      ],
      "raw_glosses": [
        "(historical) The pre-American Civil War anti-slavery resistance movement dedicated to helping escaped slaves to reach safe territory."
      ],
      "tags": [
        "historical"
      ]
    }
  ],
  "word": "Underground Railroad"
}

{
  "derived": [
    {
      "word": "underground railroad"
    }
  ],
  "forms": [
    {
      "form": "the Underground Railroad",
      "tags": [
        "canonical"
      ]
    },
    {
      "form": "Underground Railway",
      "tags": [
        "alternative"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "def": "1",
        "head": "Underground Railroad"
      },
      "expansion": "the Underground Railroad",
      "name": "en-proper noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "name",
  "senses": [
    {
      "categories": [
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English proper nouns",
        "English terms with historical senses",
        "English uncountable nouns",
        "Pages with 1 entry",
        "Pages with entries",
        "en:History of the United States",
        "en:Slavery",
        "en:Transport"
      ],
      "glosses": [
        "The pre-American Civil War anti-slavery resistance movement dedicated to helping escaped slaves to reach safe territory."
      ],
      "links": [
        [
          "American Civil War",
          "American Civil War"
        ],
        [
          "slavery",
          "slavery"
        ],
        [
          "resistance",
          "resistance"
        ],
        [
          "movement",
          "movement"
        ]
      ],
      "raw_glosses": [
        "(historical) The pre-American Civil War anti-slavery resistance movement dedicated to helping escaped slaves to reach safe territory."
      ],
      "tags": [
        "historical"
      ]
    }
  ],
  "word": "Underground Railroad"
}