"AB" meaning in Universeel taalgebruik

{
  "categories": [
    {
      "kind": "other",
      "name": "Symbool",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Woorden in het universeel taalgebruik",
      "parents": [],
      "source": "w"
    }
  ],
  "lang": "Universeel taalgebruik",
  "lang_code": "unknown",
  "pos": "symbol",
  "pos_title": "Symbool",
  "related": [
    {
      "word": "A"
    },
    {
      "word": "B"
    },
    {
      "word": "O"
    }
  ],
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Medisch_in_het_universeel taalgebruik",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "het symbool voor een bepaalde bloedgroep"
      ],
      "id": "nl-AB-unknown-symbol-4EUpYpKm",
      "topics": [
        "medicine"
      ]
    }
  ],
  "word": "AB"
}

{
  "categories": [
    "Symbool",
    "Woorden in het universeel taalgebruik"
  ],
  "lang": "Universeel taalgebruik",
  "lang_code": "unknown",
  "pos": "symbol",
  "pos_title": "Symbool",
  "related": [
    {
      "word": "A"
    },
    {
      "word": "B"
    },
    {
      "word": "O"
    }
  ],
  "senses": [
    {
      "categories": [
        "Medisch_in_het_universeel taalgebruik"
      ],
      "glosses": [
        "het symbool voor een bepaalde bloedgroep"
      ],
      "topics": [
        "medicine"
      ]
    }
  ],
  "word": "AB"
}