"double-struck" meaning in English

{
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "double-struck (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
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          "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": "Typography",
          "orig": "en:Typography",
          "parents": [
            "Printing",
            "Writing",
            "Industries",
            "Human behaviour",
            "Language",
            "Business",
            "Human",
            "Communication",
            "Economics",
            "Society",
            "All topics",
            "Social sciences",
            "Fundamental",
            "Sciences"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "Formed in a blackboard bold typeface, in which certain lines of the character are doubled"
      ],
      "id": "en-double-struck-en-adj-KTQidmM6",
      "links": [
        [
          "typography",
          "typography"
        ],
        [
          "blackboard bold",
          "blackboard bold"
        ]
      ],
      "raw_glosses": [
        "(typography, of a character or font) Formed in a blackboard bold typeface, in which certain lines of the character are doubled"
      ],
      "raw_tags": [
        "of a character or font"
      ],
      "tags": [
        "not-comparable"
      ],
      "topics": [
        "media",
        "publishing",
        "typography"
      ]
    }
  ],
  "word": "double-struck"
}

{
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "double-struck (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        "English adjectives",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English uncomparable adjectives",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Typography"
      ],
      "glosses": [
        "Formed in a blackboard bold typeface, in which certain lines of the character are doubled"
      ],
      "links": [
        [
          "typography",
          "typography"
        ],
        [
          "blackboard bold",
          "blackboard bold"
        ]
      ],
      "raw_glosses": [
        "(typography, of a character or font) Formed in a blackboard bold typeface, in which certain lines of the character are doubled"
      ],
      "raw_tags": [
        "of a character or font"
      ],
      "tags": [
        "not-comparable"
      ],
      "topics": [
        "media",
        "publishing",
        "typography"
      ]
    }
  ],
  "word": "double-struck"
}