"undreamt-of" meaning in English

{
  "forms": [
    {
      "form": "more undreamt-of",
      "tags": [
        "comparative"
      ]
    },
    {
      "form": "most undreamt-of",
      "tags": [
        "superlative"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "undreamt-of (comparative more undreamt-of, superlative most undreamt-of)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "alt_of": [
        {
          "word": "undreamed-of"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "2011, John Bradley, Cadbury's Purple Reign: The Story Behind Chocolate's Best-Loved Brand",
          "text": "Their business model of the 1920s and 1930s, which had catapulted the business to undreamt-of heights, had then turned into something of a ball and chain.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "Alternative spelling of undreamed-of."
      ],
      "id": "en-undreamt-of-en-adj-Lb255NZh",
      "links": [
        [
          "undreamed-of",
          "undreamed-of#English"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative"
      ]
    }
  ],
  "word": "undreamt-of"
}

{
  "forms": [
    {
      "form": "more undreamt-of",
      "tags": [
        "comparative"
      ]
    },
    {
      "form": "most undreamt-of",
      "tags": [
        "superlative"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "undreamt-of (comparative more undreamt-of, superlative most undreamt-of)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "alt_of": [
        {
          "word": "undreamed-of"
        }
      ],
      "categories": [
        "English adjectives",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English terms with quotations"
      ],
      "examples": [
        {
          "ref": "2011, John Bradley, Cadbury's Purple Reign: The Story Behind Chocolate's Best-Loved Brand",
          "text": "Their business model of the 1920s and 1930s, which had catapulted the business to undreamt-of heights, had then turned into something of a ball and chain.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "Alternative spelling of undreamed-of."
      ],
      "links": [
        [
          "undreamed-of",
          "undreamed-of#English"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative"
      ]
    }
  ],
  "word": "undreamt-of"
}