"barrel roof" meaning in English

{
  "forms": [
    {
      "form": "barrel roofs",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "barrel roof (plural barrel roofs)",
      "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": "Architecture",
          "orig": "en:Architecture",
          "parents": [
            "Applied sciences",
            "Art",
            "Sciences",
            "Culture",
            "All topics",
            "Society",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A roof having a semicircular cross section; used to span large distances in railway stations etc"
      ],
      "id": "en-barrel_roof-en-noun-Mut6S40~",
      "links": [
        [
          "architecture",
          "architecture"
        ],
        [
          "semicircular",
          "semicircular"
        ],
        [
          "cross section",
          "cross section"
        ],
        [
          "railway station",
          "railway station"
        ]
      ],
      "raw_glosses": [
        "(architecture) A roof having a semicircular cross section; used to span large distances in railway stations etc"
      ],
      "related": [
        {
          "word": "barrel vault"
        }
      ],
      "topics": [
        "architecture"
      ]
    }
  ],
  "word": "barrel roof"
}

{
  "forms": [
    {
      "form": "barrel roofs",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "barrel roof (plural barrel roofs)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "barrel vault"
    }
  ],
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Architecture"
      ],
      "glosses": [
        "A roof having a semicircular cross section; used to span large distances in railway stations etc"
      ],
      "links": [
        [
          "architecture",
          "architecture"
        ],
        [
          "semicircular",
          "semicircular"
        ],
        [
          "cross section",
          "cross section"
        ],
        [
          "railway station",
          "railway station"
        ]
      ],
      "raw_glosses": [
        "(architecture) A roof having a semicircular cross section; used to span large distances in railway stations etc"
      ],
      "topics": [
        "architecture"
      ]
    }
  ],
  "word": "barrel roof"
}