"fourth class" meaning in English

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      "expansion": "fourth class (uncountable)",
      "name": "en-noun"
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  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
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          "_dis": "82 18",
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      "glosses": [
        "A (former) class of mail in the United States and Canada."
      ],
      "id": "en-fourth_class-en-noun-vxU4UFSA",
      "links": [
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          "mail",
          "mail"
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          "United States",
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          "Canada",
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          "langcode": "en",
          "name": "Rail transportation",
          "orig": "en:Rail transportation",
          "parents": [
            "Transport",
            "All topics",
            "Fundamental"
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      "examples": [
        {
          "ref": "1946 May and June, “Notes and News: Russian Coach Colours”, in Railway Magazine, pages 184–185:",
          "text": "[…] Mr. S. C. Hawtrey writes that when he knew the Moscow-Kazan Railway (then under British management) in 1913, it was a regular practice in Russia to paint the exterior of first class coaches blue, second class yellow, third class green, and fourth class, where it still survived, brown.",
          "type": "quote"
        }
      ],
      "glosses": [
        "A class of rail travel formerly found in some countries."
      ],
      "id": "en-fourth_class-en-noun-sKKXIlEr",
      "links": [
        [
          "rail transport",
          "rail transport"
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      "raw_glosses": [
        "(rail transport) A class of rail travel formerly found in some countries."
      ],
      "tags": [
        "uncountable"
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      "topics": [
        "rail-transport",
        "railways",
        "transport"
      ]
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  "word": "fourth class"
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      "expansion": "fourth class (uncountable)",
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  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "glosses": [
        "A (former) class of mail in the United States and Canada."
      ],
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        [
          "mail",
          "mail"
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          "United States",
          "United States"
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        "en:Rail transportation"
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          "ref": "1946 May and June, “Notes and News: Russian Coach Colours”, in Railway Magazine, pages 184–185:",
          "text": "[…] Mr. S. C. Hawtrey writes that when he knew the Moscow-Kazan Railway (then under British management) in 1913, it was a regular practice in Russia to paint the exterior of first class coaches blue, second class yellow, third class green, and fourth class, where it still survived, brown.",
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        }
      ],
      "glosses": [
        "A class of rail travel formerly found in some countries."
      ],
      "links": [
        [
          "rail transport",
          "rail transport"
        ]
      ],
      "raw_glosses": [
        "(rail transport) A class of rail travel formerly found in some countries."
      ],
      "tags": [
        "uncountable"
      ],
      "topics": [
        "rail-transport",
        "railways",
        "transport"
      ]
    }
  ],
  "word": "fourth class"
}