"might-have-been" meaning in English

{
  "forms": [
    {
      "form": "might-have-beens",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "might-have-been (plural might-have-beens)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "1960 March, J. P. Wilson, E. N. C. Haywood, “The route through the Peak - Derby to Manchester: Part One”, in Trains Illustrated, page 157",
          "text": "One of the might-have-beens of railway history, however, would have altered the appearance of Monsal Dale considerably. The western portion of the Lancashire, Derbyshire & East Coast Railway (projected in 1891), from Chesterfield to Warrington, was planned to cross the dale and the Midland Line by a viaduct 543 yds. long and 272 ft. above the bed of the River Wye.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "Someone or something whose potential greatness was not achieved."
      ],
      "id": "en-might-have-been-en-noun-LykuwF7W",
      "synonyms": [
        {
          "word": "could-have-been"
        }
      ]
    }
  ],
  "word": "might-have-been"
}

{
  "forms": [
    {
      "form": "might-have-beens",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "might-have-been (plural might-have-beens)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "English terms with quotations"
      ],
      "examples": [
        {
          "ref": "1960 March, J. P. Wilson, E. N. C. Haywood, “The route through the Peak - Derby to Manchester: Part One”, in Trains Illustrated, page 157",
          "text": "One of the might-have-beens of railway history, however, would have altered the appearance of Monsal Dale considerably. The western portion of the Lancashire, Derbyshire & East Coast Railway (projected in 1891), from Chesterfield to Warrington, was planned to cross the dale and the Midland Line by a viaduct 543 yds. long and 272 ft. above the bed of the River Wye.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "Someone or something whose potential greatness was not achieved."
      ]
    }
  ],
  "synonyms": [
    {
      "word": "could-have-been"
    }
  ],
  "word": "might-have-been"
}