"Brocken spectre" meaning in English

{
  "etymology_text": "Named after the Brocken, a peak in the Harz Mountains in Germany.",
  "forms": [
    {
      "form": "Brocken spectres",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "Brocken spectre (plural Brocken spectres)",
      "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"
        },
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          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
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          "source": "w"
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      ],
      "glosses": [
        "Synonym of mountain spectre"
      ],
      "id": "en-Brocken_spectre-en-noun-16IO~Zv~",
      "links": [
        [
          "mountain spectre",
          "mountain spectre#English"
        ]
      ],
      "synonyms": [
        {
          "tags": [
            "synonym",
            "synonym-of"
          ],
          "word": "mountain spectre"
        }
      ]
    }
  ],
  "word": "Brocken spectre"
}

{
  "etymology_text": "Named after the Brocken, a peak in the Harz Mountains in Germany.",
  "forms": [
    {
      "form": "Brocken spectres",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "Brocken spectre (plural Brocken spectres)",
      "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",
        "Pages with 1 entry",
        "Pages with entries"
      ],
      "glosses": [
        "Synonym of mountain spectre"
      ],
      "links": [
        [
          "mountain spectre",
          "mountain spectre#English"
        ]
      ],
      "synonyms": [
        {
          "tags": [
            "synonym",
            "synonym-of"
          ],
          "word": "mountain spectre"
        }
      ]
    }
  ],
  "word": "Brocken spectre"
}