"4-6-4" meaning in English

{
  "forms": [
    {
      "form": "4-6-4s",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "4-6-4 (plural 4-6-4s)",
      "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"
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          "source": "w"
        },
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          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Rail transportation",
          "orig": "en:Rail transportation",
          "parents": [
            "Transport",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "Under the Whyte notation system, a steam locomotive that has four leading wheels arranged in a leading truck, six coupled driving wheels and four trailing wheels in a trailing truck."
      ],
      "id": "en-4-6-4-en-noun-FN9QDD7-",
      "links": [
        [
          "steam locomotive",
          "steam locomotive"
        ],
        [
          "leading wheel",
          "leading wheel"
        ],
        [
          "leading truck",
          "leading truck"
        ],
        [
          "driving wheel",
          "driving wheel"
        ],
        [
          "trailing wheel",
          "trailing wheel"
        ],
        [
          "trailing truck",
          "trailing truck"
        ]
      ]
    }
  ],
  "word": "4-6-4"
}

{
  "forms": [
    {
      "form": "4-6-4s",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "4-6-4 (plural 4-6-4s)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
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        "English terms spelled with numbers",
        "English words without vowels",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Rail transportation"
      ],
      "glosses": [
        "Under the Whyte notation system, a steam locomotive that has four leading wheels arranged in a leading truck, six coupled driving wheels and four trailing wheels in a trailing truck."
      ],
      "links": [
        [
          "steam locomotive",
          "steam locomotive"
        ],
        [
          "leading wheel",
          "leading wheel"
        ],
        [
          "leading truck",
          "leading truck"
        ],
        [
          "driving wheel",
          "driving wheel"
        ],
        [
          "trailing wheel",
          "trailing wheel"
        ],
        [
          "trailing truck",
          "trailing truck"
        ]
      ]
    }
  ],
  "word": "4-6-4"
}