"back board" meaning in English

{
  "forms": [
    {
      "form": "back boards",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "back board (plural back boards)",
      "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": "Curling",
          "orig": "en:Curling",
          "parents": [
            "Winter sports",
            "Sports",
            "Winter activities",
            "Human activity",
            "Winter",
            "Human behaviour",
            "Seasons",
            "Human",
            "Nature",
            "Periodic occurrences",
            "All topics",
            "Time",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "The border at the extreme ends of the sheet."
      ],
      "id": "en-back_board-en-noun-vmxozvPU",
      "links": [
        [
          "curling",
          "curling"
        ],
        [
          "border",
          "border"
        ],
        [
          "sheet",
          "sheet"
        ]
      ],
      "raw_glosses": [
        "(curling) The border at the extreme ends of the sheet."
      ],
      "topics": [
        "ball-games",
        "curling",
        "games",
        "hobbies",
        "lifestyle",
        "sports"
      ]
    }
  ],
  "word": "back board"
}

{
  "forms": [
    {
      "form": "back boards",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "back board (plural back boards)",
      "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:Curling"
      ],
      "glosses": [
        "The border at the extreme ends of the sheet."
      ],
      "links": [
        [
          "curling",
          "curling"
        ],
        [
          "border",
          "border"
        ],
        [
          "sheet",
          "sheet"
        ]
      ],
      "raw_glosses": [
        "(curling) The border at the extreme ends of the sheet."
      ],
      "topics": [
        "ball-games",
        "curling",
        "games",
        "hobbies",
        "lifestyle",
        "sports"
      ]
    }
  ],
  "word": "back board"
}