"open-topper" meaning in English

{
  "forms": [
    {
      "form": "open-toppers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "open-topper (plural open-toppers)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "British English",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Vehicles",
          "orig": "en:Vehicles",
          "parents": [
            "Machines",
            "Transport",
            "Technology",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A double-deck bus with an open, or partially open, top deck."
      ],
      "id": "en-open-topper-en-noun-BRii~HfV",
      "links": [
        [
          "double-deck",
          "double-decker"
        ],
        [
          "bus",
          "bus"
        ]
      ],
      "raw_glosses": [
        "(UK) A double-deck bus with an open, or partially open, top deck."
      ],
      "related": [
        {
          "word": "open-top"
        },
        {
          "word": "open-topped"
        }
      ],
      "synonyms": [
        {
          "word": "open topper"
        },
        {
          "word": "open-top bus"
        }
      ],
      "tags": [
        "UK"
      ]
    }
  ],
  "word": "open-topper"
}

{
  "forms": [
    {
      "form": "open-toppers",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "open-topper (plural open-toppers)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "open-top"
    },
    {
      "word": "open-topped"
    }
  ],
  "senses": [
    {
      "categories": [
        "British English",
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "en:Vehicles"
      ],
      "glosses": [
        "A double-deck bus with an open, or partially open, top deck."
      ],
      "links": [
        [
          "double-deck",
          "double-decker"
        ],
        [
          "bus",
          "bus"
        ]
      ],
      "raw_glosses": [
        "(UK) A double-deck bus with an open, or partially open, top deck."
      ],
      "tags": [
        "UK"
      ]
    }
  ],
  "synonyms": [
    {
      "word": "open topper"
    },
    {
      "word": "open-top bus"
    }
  ],
  "word": "open-topper"
}