"air defence" meaning in English

{
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    {
      "form": "air defences",
      "tags": [
        "plural"
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  "head_templates": [
    {
      "args": {
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      "expansion": "air defence (countable and uncountable, plural air defences)",
      "name": "en-noun"
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  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "air defense"
        }
      ],
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          "name": "English entries with incorrect language header",
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          "source": "w"
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      "glosses": [
        "Alternative spelling of air defense"
      ],
      "id": "en-air_defence-en-noun-gZUqqTs7",
      "links": [
        [
          "air defense",
          "air defense#English"
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      ],
      "tags": [
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    }
  ],
  "word": "air defence"
}

{
  "forms": [
    {
      "form": "air defences",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "~"
      },
      "expansion": "air defence (countable and uncountable, plural air defences)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "alt_of": [
        {
          "word": "air defense"
        }
      ],
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English uncountable nouns",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "glosses": [
        "Alternative spelling of air defense"
      ],
      "links": [
        [
          "air defense",
          "air defense#English"
        ]
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      "tags": [
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  "word": "air defence"
}