"unheard of" meaning in English

{
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "unheard of (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "used as predicative",
          "word": "unheard-of"
        }
      ],
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English negative polarity items",
          "parents": [
            "Negative polarity items",
            "Terms by semantic function"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "1952 October, C. A. Johns, “One Hundred Years at Kings Cross—1”, in Railway Magazine, pages 650-651:",
          "text": "Such was the station provided for the infrequent services of 1852, when suburban traffic was unheard of, and Hornsey, Colney Hatch & Southgate, Barnet, and Potters Bar were the only intermediate stations on the 17¾ miles between London and Hatfield.",
          "type": "quote"
        }
      ],
      "glosses": [
        "Alternative spelling of unheard-of (used as predicative)"
      ],
      "id": "en-unheard_of-en-adj-LH0nQeWo",
      "links": [
        [
          "unheard-of",
          "unheard-of#English"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative",
        "not-comparable"
      ]
    }
  ],
  "word": "unheard of"
}

{
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "unheard of (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "alt_of": [
        {
          "extra": "used as predicative",
          "word": "unheard-of"
        }
      ],
      "categories": [
        "English adjectives",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English negative polarity items",
        "English terms with quotations",
        "English uncomparable adjectives",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "examples": [
        {
          "ref": "1952 October, C. A. Johns, “One Hundred Years at Kings Cross—1”, in Railway Magazine, pages 650-651:",
          "text": "Such was the station provided for the infrequent services of 1852, when suburban traffic was unheard of, and Hornsey, Colney Hatch & Southgate, Barnet, and Potters Bar were the only intermediate stations on the 17¾ miles between London and Hatfield.",
          "type": "quote"
        }
      ],
      "glosses": [
        "Alternative spelling of unheard-of (used as predicative)"
      ],
      "links": [
        [
          "unheard-of",
          "unheard-of#English"
        ]
      ],
      "tags": [
        "alt-of",
        "alternative",
        "not-comparable"
      ]
    }
  ],
  "word": "unheard of"
}