"burr hole" meaning in English

{
  "forms": [
    {
      "form": "burr holes",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "burr hole (plural burr holes)",
      "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": "Surgery",
          "orig": "en:Surgery",
          "parents": [
            "Medicine",
            "Biology",
            "Healthcare",
            "Sciences",
            "Health",
            "All topics",
            "Body",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A hole drilled into the cranium"
      ],
      "id": "en-burr_hole-en-noun-J-8jDmAT",
      "links": [
        [
          "surgery",
          "surgery"
        ],
        [
          "hole",
          "hole"
        ],
        [
          "cranium",
          "cranium"
        ]
      ],
      "raw_glosses": [
        "(surgery) A hole drilled into the cranium"
      ],
      "topics": [
        "medicine",
        "sciences",
        "surgery"
      ]
    }
  ],
  "word": "burr hole"
}

{
  "forms": [
    {
      "form": "burr holes",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "burr hole (plural burr holes)",
      "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",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Surgery"
      ],
      "glosses": [
        "A hole drilled into the cranium"
      ],
      "links": [
        [
          "surgery",
          "surgery"
        ],
        [
          "hole",
          "hole"
        ],
        [
          "cranium",
          "cranium"
        ]
      ],
      "raw_glosses": [
        "(surgery) A hole drilled into the cranium"
      ],
      "topics": [
        "medicine",
        "sciences",
        "surgery"
      ]
    }
  ],
  "word": "burr hole"
}