"hard as iron" meaning in English

{
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "hard as iron (not comparable)",
      "name": "en-adj"
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  ],
  "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"
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          "kind": "other",
          "name": "English similes",
          "parents": [],
          "source": "w"
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      ],
      "examples": [
        {
          "ref": "2006, Nancy M. Tischler, All Things in the Bible, page 411",
          "text": "The Torah notes that a teacher of the law must be as hard as iron.",
          "type": "quotation"
        },
        {
          "ref": "2011, Gillian Clarke, At the Source: A Writer's Year",
          "text": "Christina Rossetti takes up the theme: In the bleak midwinter Frosty wind made moan, Earth stood hard as iron, Water like a stone, Snow had fallen, snow on snow, Snow on snow, In the bleak midwinter Long ago",
          "type": "quotation"
        },
        {
          "ref": "2014, Stephanie Draven, Poisoned Kisses",
          "text": "“If you tried to tell me what to do, we'd only end up engaged in a fierce battle of wills.” She felt him smirk against her neck. “Mine is hard as iron.” His will. He meant his will was hard as iron.",
          "type": "quotation"
        },
        {
          "ref": "2015, Lee Bond, Dark Iron King I: Thy King's Will Be Done",
          "text": "A simple rap on the forehead with a fist hard as iron and their Fishy-Fish blacksmith would down for the count.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "very hard"
      ],
      "id": "en-hard_as_iron-en-adj-UF8f5ykm",
      "links": [
        [
          "hard",
          "hard"
        ]
      ],
      "qualifier": "simile",
      "raw_glosses": [
        "(simile) very hard"
      ],
      "tags": [
        "not-comparable"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-hard as iron.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/c/c2/En-au-hard_as_iron.ogg/En-au-hard_as_iron.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/c/c2/En-au-hard_as_iron.ogg",
      "tags": [
        "Australia"
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      "text": "Audio (AU)"
    }
  ],
  "word": "hard as iron"
}

{
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "hard as iron (not comparable)",
      "name": "en-adj"
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  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        "English adjectives",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English similes",
        "English terms with audio links",
        "English terms with quotations",
        "English uncomparable adjectives"
      ],
      "examples": [
        {
          "ref": "2006, Nancy M. Tischler, All Things in the Bible, page 411",
          "text": "The Torah notes that a teacher of the law must be as hard as iron.",
          "type": "quotation"
        },
        {
          "ref": "2011, Gillian Clarke, At the Source: A Writer's Year",
          "text": "Christina Rossetti takes up the theme: In the bleak midwinter Frosty wind made moan, Earth stood hard as iron, Water like a stone, Snow had fallen, snow on snow, Snow on snow, In the bleak midwinter Long ago",
          "type": "quotation"
        },
        {
          "ref": "2014, Stephanie Draven, Poisoned Kisses",
          "text": "“If you tried to tell me what to do, we'd only end up engaged in a fierce battle of wills.” She felt him smirk against her neck. “Mine is hard as iron.” His will. He meant his will was hard as iron.",
          "type": "quotation"
        },
        {
          "ref": "2015, Lee Bond, Dark Iron King I: Thy King's Will Be Done",
          "text": "A simple rap on the forehead with a fist hard as iron and their Fishy-Fish blacksmith would down for the count.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "very hard"
      ],
      "links": [
        [
          "hard",
          "hard"
        ]
      ],
      "qualifier": "simile",
      "raw_glosses": [
        "(simile) very hard"
      ],
      "tags": [
        "not-comparable"
      ]
    }
  ],
  "sounds": [
    {
      "audio": "En-au-hard as iron.ogg",
      "mp3_url": "https://upload.wikimedia.org/wikipedia/commons/transcoded/c/c2/En-au-hard_as_iron.ogg/En-au-hard_as_iron.ogg.mp3",
      "ogg_url": "https://upload.wikimedia.org/wikipedia/commons/c/c2/En-au-hard_as_iron.ogg",
      "tags": [
        "Australia"
      ],
      "text": "Audio (AU)"
    }
  ],
  "word": "hard as iron"
}